Resist composition and method for producing resist pattern

ABSTRACT

Disclosed is a resist composition including a compound represented by formula (I), a resin having an acid-labile group and an acid generator:wherein, in formula (I),R1 represents a halogen atom or an alkyl fluoride group having 1 to 6 carbon atoms,m1 represents an integer of 1 to 5, and when m1 is 2 or more, a plurality of R1 may be the same or different from each other.

BACKGROUND OF THE INVENTION Technical Field

The present disclosure relates to a resist composition and a method forproducing a resist pattern which uses the resist composition.

Description of the Related Art

JP2000-066406A mentions a resist composition including a compound of thefollowing structural formula, a resin having an acid-labile group and anacid generator.

SUMMARY OF THE INVENTION

An object is to provide resist composition including a compound capableof producing a resist pattern with CD uniformity (CDU) which is betterthan that of a resist pattern formed from the resist compositionincluding the compound mentioned above.

The present disclosure includes the following resist compositions.

[1] A resist composition comprising a compound represented by formula(I), a resin having an acid-labile group and an acid generator:

wherein, in formula (I),

R¹ represents a halogen atom or an alkyl fluoride group having 1 to 6carbon atoms,

m1 represents an integer of 1 to 5, and when m1 is 2 or more, aplurality of R¹ may be the same or different from each other.

[2] The resist composition according to [1], wherein R¹ is a fluorineatom, an iodine atom or a trifluoromethyl group.

[3] The resist composition according to [1] or [2], wherein the m1 is aninteger of 1 to 3.

[4] The resist composition according to any one of [1] to [3], whereinthe R¹ includes at least an iodine atom.

[5] The resist composition according to any one of [1] to [4], whereinthe content of the compound (I) is 0.001 to 20% by mass based on thesolid content.

[6] The resist composition according to any one of [1] to [5], whereinthe resin having an acid-labile group includes at least one selectedfrom the group consisting of a structural unit represented by formula(a1-1) and a structural unit represented by formula (a1-2):

wherein, in formula (a1-1) and formula (a1-2),

L^(a1) and L^(a2) each independently represent —O— or*—O—(CH₂)_(k1)—CO—O—, and k1 represents an integer of 1 to 7, *represents a bond to —CO—.

R^(a4) and R^(a5) each independently represent a hydrogen atom, ahalogen atom, or an alkyl group having 1 to 6 carbon atoms which mayhave a halogen atom,

R^(a6) and R^(a7) each independently represent an alkyl group having 1to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, analicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatichydrocarbon group having 6 to 18 carbon atoms, or a group obtained bycombining these groups,

m1 represents an integer of 0 to 14,

n1 represents an integer of 0 to 10, and

n1′ represents an integer of 0 to 3.

[7] The resist composition according to any one of [1] to [6], whereinthe resin having an acid-labile group further includes a structural unitrepresented by formula (a2-A):

wherein, in formula (a2-A),

R^(a50) represents a hydrogen atom, a halogen atom, or an alkyl grouphaving 1 to 6 carbon atoms which may have a halogen atom,

R^(a51) represents a halogen atom, a hydroxy group, an alkyl grouphaving 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms,an alkoxyalkyl group having 2 to 12 carbon atoms, an alkoxyalkoxy grouphaving 2 to 12 carbon atoms, an alkylcarbonyl group having 2 to 4 carbonatoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, anacryloyloxy group or a methacryloyloxy group,

A^(a50) represents a single bond or *—X^(a51)-(A^(a52)-X^(a52)) and *represents a bond to carbon atoms to which —R^(a50) is bonded,

A^(a52) represents an alkanediyl group having 1 to 6 carbon atoms,

X^(a51) and X^(a52) each independently represent —O—, —CO—O— or —O—CO—,

nb represents 0 or 1, and

mb represents an integer of 0 to 4, and when mb is an integer of 2 ormore, a plurality of R^(a51) may be the same or different from eachother.

[8] The resist composition according to any one of [1] to [7], whereinthe acid generator includes a salt represented by formula (B1):

wherein, in formula (B1),

Q^(b1) and Q^(b2) each independently represent a fluorine atom or aperfluoroalkyl group having 1 to 6 carbon atoms,

L^(b1) represents a divalent saturated hydrocarbon group having 1 to 24carbon atoms, —CH₂— included in the divalent saturated hydrocarbon groupmay be replaced by —O— or —CO—, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group,

Y represents a methyl group which may have a substituent, or analicyclic hydrocarbon group having 3 to 24 carbon atoms which may have asubstituent, and —CH₂— included in the alicyclic hydrocarbon group maybe replaced by —O—, —S(O)₂— or —CO—, and

Z⁺ represents an organic cation.

[9] The resist composition according to any one of [1] to [8], furthercomprising a salt generating an acid having an acidity lower than thatof an acid generated from the acid generator.

The present disclosure also includes the following method for producinga resist pattern.

[10] A method for producing a resist pattern, which comprises:

(1) a step of applying the resist composition according to any one of[1] to [9] on a substrate,

(2) a step of drying the applied resist composition to form acomposition layer,

(3) a step of exposing the composition layer,

(4) a step of heating the exposed composition layer, and

(5) a step of developing the heated composition layer.

It is possible to produce a resist pattern with satisfactory CDuniformity (CDU) by using a resist composition using compounds accordingto at least some embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present specification, “(meth)acrylic monomer” means at least oneselected from the group consisting of a monomer having a structure of“CH₂═CH—CO—” and a monomer having a structure of “CH₂═C(CH₃)—CO—”.Similarly, “(meth)acrylate” and “(meth)acrylic acid” each mean “at leastone selected from the group consisting of acrylate and methacrylate” and“at least one selected from the group consisting of acrylic acid andmethacrylic acid”. When a structural unit having “CH₂═C(CH₃)—CO—” or“CH₂═CH—CO—” is exemplified, a structural unit having both groups shallbe similarly exemplified. “Derived” means that a polymerizable C═C bondincluded in the molecule becomes a —C—C— group by polymerization. Ingroups mentioned in the present specification, regarding groups capableof having both a linear structure and a branched structure, they mayhave either the linear or branched structure. “Combined group” means agroup in which two or more exemplified groups are bonded, and valencesof those groups may be appropriately changed depending on a bondingform. When stereoisomers exist, all stereoisomers are included.

In the present specification, “solid content of resist composition”means the total of contents in which the below-mentioned solvent (E) isremoved from the total amount of the resist composition.

<Resist Composition>

The resist composition according to some embodiments of the presentdisclosure includes a compound represented by formula (I) (hereinaftersometimes referred to as “compound (I)”), a resin having an acid-labilegroup (hereinafter sometimes referred to as “resin (A)”) and an acidgenerator (hereinafter sometimes referred to as “acid generator (B)”).The “acid-labile group” means a group having a leaving group which iseliminated by contact with an acid, thus converting into aconstitutional unit having a hydrophilic group (e.g. a hydroxy group ora carboxy group).

The resist composition according to some embodiments of the presentdisclosure may further include a resin other than the resin (A).

The resist composition according to some embodiments of the presentdisclosure preferably includes a quencher such as a salt generating anacid having an acidity lower than that of an acid generated from theacid generator (hereinafter sometimes referred to as “quencher (C)”),and preferably includes a solvent (hereinafter sometimes referred to as“solvent (E)”).

<Compound (I)>

The resist composition according to some embodiments of the presentdisclosure includes a compound (I):

wherein, in formula (I), all symbols are the same as defined above.

Examples of the halogen atom as for R¹ include a fluorine atom, achlorine atom, an iodine atom and a bromine atom.

Examples of the alkyl fluoride group having 1 to 6 carbon atoms as forR¹ include alkyl fluoride groups such as a trifluoromethyl group, adifluoromethyl group, a perfluoroethyl group, a 2,2,2-trifluoroethylgroup, a 1,1,2,2-tetrafluoroethyl group, a perfluoropropyl group, a2,2,3,3,3-pentafluoropropyl group, a perfluorobutyl group, a1,1,2,2,3,3,4,4-octafluorobutyl group, a perfluoropentyl group, a2,2,3,3,4,4,5,5,5-nonafluoropentyl group and a perfluorohexyl group.

m1 is preferably an integer of 1 to 3.

R¹ is preferably a fluorine atom, an iodine atom or a perfluoroalkylgroup having 1 to 3 carbon atoms, more preferably a fluorine atom, aniodine atom or a trifluoromethyl group, and still more preferably afluorine atom or an iodine atom.

When m1 is 1, R¹ is preferably bonded to the ortho-position or themeta-position, and more preferably the ortho-position, with respect to acarboxy group of the benzene ring.

Examples of the compound (I) include compounds represented by thefollowing formulas.

The content of the compound (I) is usually 0.001 to 20% by mass,preferably 0.005 to 15% by mass, and more preferably 0.01 to 10% bymass, based on the solid content of the resist composition.

<Resin (A)>

The resin (A) includes a structural unit having an acid-labile group(hereinafter sometimes referred to as “structural unit (a1)”). It ispreferable that the resin (A) further includes a structural unit otherthan the structural unit (a1). Examples of the structural unit otherthan the structural unit (a1) include a structural unit having noacid-labile group (hereinafter sometimes referred to as “structural unit(s)”), a structural unit other than the structural unit (a1) and thestructural unit (s) (e.g. a structural unit having a halogen atommentioned later (hereinafter sometimes referred to as “structural unit(a4)”), a structural unit having a non-leaving hydrocarbon groupmentioned later (hereinafter sometimes referred to as “structural unit(a5)) and other structural units derived from monomers known in the art.

<Structural Unit (a1)>

The structural unit (a1) is derived from a monomer having an acid-labilegroup (hereinafter sometimes referred to as “monomer (a1)”).

The acid-labile group contained in the resin (A) is preferably a grouprepresented by formula (1) (hereinafter also referred to as group (1))and/or a group represented by formula (2) (hereinafter also referred toas group (2)):

wherein, in formula (1), R^(a1), R^(a2) and R^(a3) each independentlyrepresent an alkyl group having 1 to 8 carbon atoms, an alkenyl grouphaving 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to20 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbonatoms, or a group obtained by combining these groups, and R^(a1) andR^(a2) are bonded to each other to form a nonaromatic hydrocarbon ringhaving 3 to 20 carbon atoms together with carbon atoms to which R^(a1)and R^(a2) are bonded,

ma and na each independently represent 0 or 1, and at least one of maand na represents 1, and

* represents a bonding site:

wherein, in formula (2), R^(a1)′ and R^(a2)′ each independentlyrepresent a hydrogen atom or a hydrocarbon group having 1 to 12 carbonatoms, R^(a3)′ represents a hydrocarbon group having 1 to 20 carbonatoms, or R^(a2)′ and R^(a3)′ are bonded to each other to form aheterocyclic ring having 3 to 20 carbon atoms together with carbon atomsand X to which R^(a2)′ and R^(a3)′ are bonded, and —CH₂— included in thehydrocarbon group and the heterocyclic ring may be replaced by —O— or—S—,

X represents an oxygen atom or a sulfur atom,

na′ represents 0 or 1, and

* represents a bonding site.

Examples of the alkyl group in R^(a1), R^(a2) and R^(a3) include amethyl group, an ethyl group, a propyl group, a butyl group, a pentylgroup, a hexyl group, a heptyl group, an octyl group and the like.

Examples of the alkenyl group in R^(a1), R^(a2) and R^(a3) include anethenyl group, a propenyl group, an isopropenyl group, a butenyl group,an isobutenyl group, a tert-butenyl group, a pentenyl group, a hexenylgroup, a heptenyl group, an octynyl group, an isooctynyl group, anonenyl group and the like.

The alicyclic hydrocarbon group in R^(a1), R^(a2) and R^(a3) may beeither monocyclic or polycyclic. Examples of the monocyclic alicyclichydrocarbon group include cycloalkyl groups such as a cyclopentyl group,a cyclohexyl group, a cycloheptyl group and a cyclooctyl group. Examplesof the polycyclic alicyclic hydrocarbon group include adecahydronaphthyl group, an adamantyl group, a norbornyl group and thefollowing groups (* represents a bonding site). The number of carbonatoms of the alicyclic hydrocarbon group of R^(a1), R^(a2) and R^(a3) ispreferably 3 to 16.

Examples of the aromatic hydrocarbon group in R^(a1), R^(a2) and R^(a3)include aryl groups such as a phenyl group, a naphthyl group, an anthrylgroup, a biphenyl group and a phenanthryl group.

Examples of the combined group include groups obtained by combining theabove-mentioned alkyl group and alicyclic hydrocarbon group (e.g.,alkylcycloalkyl groups or cycloalkylalkyl groups such asmethylcyclohexyl groups, dimethylcyclohexyl groups, methylnorbornylgroups, cyclohexylmethyl groups, adamantylmethyl groups,adamantyldimethyl groups, and norbornylethyl groups), aralkyl groupssuch as a benzyl group, aromatic hydrocarbon groups such as an alkylgroup (a p-methylphenyl group, a p-tert-butylphenyl group, a tolylgroup, a xylyl group, a cumenyl group, a mesityl group, a2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group, etc.), aromatichydrocarbon groups having an alicyclic hydrocarbon group (ap-cyclohexylphenyl group, a p-adamantylphenyl group, etc.),aryl-cycloalkyl groups such as a phenylcyclohexyl group, and the like.

Preferably, ma is 0 and na is 1.

When R^(a1) and R^(a2) are bonded to each other to form a nonaromatichydrocarbon ring, examples of —C(R^(a1))(R^(a2))(R^(a3)) include thefollowing rings. The nonaromatic hydrocarbon ring preferably has 3 to 12carbon atoms. * represents a bonding site to —O—.

Examples of the hydrocarbon group in R^(a1)′, R^(a2)′ and R^(a3)′include an alkyl group, an alicyclic hydrocarbon group, an aromatichydrocarbon group, and groups formed by combining these groups.

Examples of the alkyl group and the alicyclic hydrocarbon group includethose which are the same as mentioned in R^(a1), R^(a2) and R^(a3).

Examples of the aromatic hydrocarbon group include aryl groups such as aphenyl group, a naphthyl group, an anthryl group, a biphenyl group and aphenanthryl group.

Examples of the combined group include groups obtained by combining theabove-mentioned alkyl group and alicyclic hydrocarbon group (e.g.,alkylcycloalkyl groups or cycloalkylalkyl groups such asmethylcyclohexyl groups, dimethylcyclohexyl groups, methylnorbornylgroups, cyclohexylmethyl groups, adamantylmethyl groups,adamantyldimethyl groups, and norbornylethyl groupscycloalkylalkylgroups), aralkyl groups such as a benzyl group, aromatic hydrocarbongroups having an alkyl group (a p-methylphenyl group, ap-tert-butylphenyl group, a tolyl group, a xylyl group, a cumenyl group,a mesityl group, a 2,6-diethylphenyl group, a 2-methyl-6-ethylphenylgroup, etc.), aromatic hydrocarbon groups having an alicyclichydrocarbon group (a p-cyclohexylphenyl group, a p-adamantylphenylgroup, etc.), aryl-cycloalkyl groups such as a phenylcyclohexyl group,and the like.

When R^(a2)′ and R^(a3)′ are bonded to each other together with carbonatoms and X to which R^(a2)′ and R^(a3)′ are bonded, examples of—C(R^(a1)′) (R^(a2)′)—X—R^(a3)′ include the following rings. *represents a bonding site.

Of R^(a1)′ and R^(a2)′, at least one is preferably a hydrogen atom.

na′ is preferably 0.

Examples of the group (1) include the following groups.

A group wherein, in formula (1), R^(a1), R^(a2) and R^(a3) are alkylgroups, ma=0 and na=1. The group is preferably a tert-butoxycarbonylgroup.

A group wherein, in formula (1), R^(a1) and R^(a2) are bonded to eachother to form an adamantyl group together with carbon atoms to whichR^(a1) and R^(a2) are bonded, R^(a3) is an alkyl group, ma=0 and na=1.

A group wherein, in formula (1), R^(a1) and R^(a2) are eachindependently an alkyl group, R^(a3) is an adamantyl group, ma=0 andna=1.

Specific examples of the group (1) include the following groups. *represents a bonding site.

Specific examples of the group (2) include the following groups. *represents a bonding site.

The monomer (a1) is preferably a monomer having an acid-labile group andan ethylenic unsaturated bond, and more preferably a (meth)acrylicmonomer having an acid-labile group.

Of the (meth)acrylic monomers having an acid-labile group, those havingan alicyclic hydrocarbon group having 5 to 20 carbon atoms arepreferably exemplified. When a resin (A) including a structural unitderived from a monomer (a1) having a bulky structure such as analicyclic hydrocarbon group is used in a resist composition, it ispossible to improve the resolution of a resist pattern.

The structural unit derived from a (meth)acrylic monomer having a group(1) is a structural unit represented by formula (a1-0) (hereinaftersometimes referred to as structural unit (a1-0)), a structural unitrepresented by formula (a1-1) (hereinafter sometimes referred to asstructural unit (a1-1)) or a structural unit represented by formula(a1-2) (hereinafter sometimes referred to as structural unit (a1-2)).Preferably, the structural unit is at least one structural unit selectedfrom the group consisting of a structural unit (a1-1) and a structuralunit (a1-2). These structural units may be used alone, or two or morestructural units may be used in combination.

In formula (a1-0), formula (a1-1) and formula (a1-2),

L^(a01), L^(a1) and L^(a2) each independently represent —O— or*—O—(CH₂)_(k1)—CO—O—, k1 represents an integer of 1 to 7, and *represents a bonding site to —CO—,

R^(a01), R^(a4) and R^(a5) each independently represent a hydrogen atom,a halogen atom, or an alkyl group having 1 to 6 carbon atoms which mayhave a halogen atom.

R^(a02), R^(a03) and R^(a04) each independently represent an alkyl grouphaving 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbonatoms, or a group obtained by combining these groups,

R^(a6) and R^(a7) each independently represent an alkyl group having 1to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, analicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatichydrocarbon group having 6 to 18 carbon atoms, or a group obtained bycombining these groups,

m1 represents an integer of 0 to 14,

n1 represents an integer of 0 to 10, and

n1′ represents an integer of 0 to 3.

R^(a01), R^(a4) and R^(a5) are preferably a hydrogen atom or a methylgroup.

L^(a01), L^(a1) and L^(a2) are preferably an oxygen atom or*—O—(CH₂)_(k01)—CO—O— (in which k01 is preferably an integer of 1 to 4,and more preferably 1), and more preferably an oxygen atom.

Examples of the alkyl group, the alkenyl group, the alicyclichydrocarbon group, the aromatic hydrocarbon group, and groups obtainedby combining these groups in R^(a02), R^(a03), R^(a04), R^(a6) andR^(a7) include the same groups as mentioned for R^(a1), R^(a2) andR^(a3) of group (1).

The alkyl group in R^(a02), R^(a03) and R^(a04) is preferably an alkylgroup having 1 to 6 carbon atoms, more preferably a methyl group or anethyl group, and still more preferably a methyl group.

The alkyl group in R^(a6) and R^(a7) is preferably an alkyl group having1 to 6 carbon atoms, more preferably a methyl group, an ethyl group, anisopropyl group or a t-butyl group, and still more preferably an ethylgroup, an isopropyl group or a t-butyl group.

The alkenyl group in R^(a6) and R^(a7) is preferably an alkenyl grouphaving 2 to 6 carbon atoms, more preferably an ethenyl group, a propenylgroup, an isopropenyl group or a butenyl group.

The number of carbon atoms of the alicyclic hydrocarbon group ofR^(a02), R^(a03), R^(a04), R^(a6) and R^(a7) is preferably 5 to 12, andmore preferably 5 to 10.

The number of carbon atoms of the aromatic hydrocarbon group of R^(a02),R^(a03), R^(a04), R^(a6) and R^(a7) is preferably 6 to 12, and morepreferably 6 to 10.

The total number of carbon atoms of the group obtained by combining thealkyl group with the alicyclic hydrocarbon group is preferably 18 orless.

The total number of carbon atoms of the group obtained by combining thealkyl group with the aromatic hydrocarbon group is preferably 18 orless.

R^(a02) and R^(a03) are preferably an alkyl group having 1 to 6 carbonatoms or an aromatic hydrocarbon group having 6 to 12 carbon atoms, andmore preferably a methyl group, an ethyl group, a phenyl group or anaphthyl group.

R^(a04) is preferably an alkyl group having 1 to 6 carbon atoms or analicyclic hydrocarbon group having 5 to 12 carbon atoms, and morepreferably a methyl group, an ethyl group, a cyclohexyl group or anadamantyl group.

Preferably, R^(a6) and R^(a7) are each independently an alkyl grouphaving 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atomsor an aromatic hydrocarbon group having 6 to 12 carbon atoms, morepreferably a methyl group, an ethyl group, an isopropyl group, a t-butylgroup, an ethenyl group, a phenyl group or a naphthyl group, and stillmore preferably an ethyl group, an isopropyl group, a t-butyl group, anethenyl group or a phenyl group.

m1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1′ is preferably 0 or 1.

The structural unit (a1-0) includes, for example, a structural unitrepresented by any one of formula (a1-0-1) to formula (a1-0-18) and astructural unit in which a methyl group corresponding to R^(a01) in thestructural unit (a1-0) is substituted with a hydrogen atom and ispreferably a structural unit represented by any one of formula (a1-0-1)to formula (a1-0-10), formula (a1-0-13) and formula (a1-0-14).

The structural unit (a1-1) includes, for example, structural unitsderived from the monomers mentioned in JP 2010-204646 A. Of thesestructural units, a structural unit represented by any one of formula(a1-1-1) to formula (a1-1-7) and a structural unit in which a methylgroup corresponding to R^(a4) in the structural unit (a1-1) issubstituted with a hydrogen atom are preferable, and a structural unitrepresented by any one of formula (a1-1-1) to formula (a1-1-4) is morepreferable.

Examples of the structural unit (a1-2) include a structural unitrepresented by any one of formula (a1-2-1) to formula (a1-2-12) and astructural unit in which a methyl group corresponding to R^(a5) in thestructural unit (a1-2) is substituted with a hydrogen atom, and astructure unit represented by any one of formula (a1-2-2), formula(a1-2-5), formula (a1-2-6) and formula (a1-2-10) to formula (a1-2-12) ispreferable.

When the resin (A) includes a structural unit (a1-0), the contentthereof is usually 5 to 80 mol %, preferably 5 to 75 mol %, and morepreferably 10 to 70 mol %, based on all structural units of the resin(A).

When the resin (A) includes a structural unit (a1-1) and/or a structuralunit (a1-2), the total content thereof is usually 10 to 90 mol %,preferably 15 to 85 mol %, more preferably 20 to 80 mol %, still morepreferably 20 to 75 mol %, and yet more preferably 20 to 70 mol %, basedon all structural units of the resin (A).

In the structural unit (a1), examples of the structural unit having agroup (2) include a structural unit represented by formula (a1-4)(hereinafter sometimes referred to as “structural unit (a1-4)”):

wherein, in formula (a1-4),

R^(a32) represents a hydrogen atom, a halogen atom or an alkyl grouphaving 1 to 6 carbon atoms which may have a halogen atom,

R^(a33) represents a halogen atom, a hydroxy group, an alkyl grouphaving 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms,an alkoxyalkyl group having 2 to 12 carbon atoms, an alkoxyalkoxy grouphaving 2 to 12 carbon atoms, an alkylcarbonyl group having 2 to 4 carbonatoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, anacryloyloxy group or a methacryloyloxy group,

A^(a30) represents a single bond or *—X^(a31)-(A^(a32)-X^(a32)) and *represents a bonding site to carbon atoms to which —R^(a32) is bonded,

A^(a32) represents an alkanediyl group having 1 to 6 carbon atoms,

X^(a31) and X^(a32) each independently represent —O—, —CO—O— or —O—CO—,

nc represents 0 or 1,

la represents an integer of 0 to 4, and when la is an integer of 2 ormore, a plurality of R^(a33) may be the same or different from eachother, and

R^(a34) and R^(a35) each independently represent a hydrogen atom or ahydrocarbon group having 1 to 12 carbon atoms, R^(a36) represents ahydrocarbon group having 1 to 20 carbon atoms, or R^(a35) and R^(a36)are bonded to each other to form a divalent hydrocarbon group having 2to 20 carbon atoms together with —C—O— to which R^(a35) and R^(a36) arebonded, and —CH₂— included in the hydrocarbon group and the divalenthydrocarbon group may be replaced by —O— or —S—.

Examples of the halogen atom in R^(a32) and R^(a33) include a fluorineatom, a chlorine atom and a bromine atom.

Examples of the alkyl group having 1 to 6 carbon atoms which may have ahalogen atom in R^(a32) include a trifluoromethyl group, adifluoromethyl group, a methyl group, a perfluoroethyl group, a2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethylgroup, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, apropyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutylgroup, a butyl group, a perfluoropentyl group, a2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl groupand a perfluorohexyl group.

R^(a32) is preferably a hydrogen atom or an alkyl group having 1 to 4carbon atoms, more preferably a hydrogen atom, a methyl group or anethyl group, and still more preferably a hydrogen atom or a methylgroup.

Examples of the alkyl group in R^(a33) include a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, a sec-butylgroup, a tert-butyl group, a pentyl group and a hexyl group.

Examples of the alkoxy group in R^(a33) include a methoxy group, anethoxy group, a propoxy group, an isopropoxy group, a butoxy group, asec-butoxy group, a tert-butoxy group, a pentyloxy group and a hexyloxygroup. The alkoxy group is preferably an alkoxy group having 1 to 4carbon atoms, more preferably a methoxy group or an ethoxy group, andstill more preferably a methoxy group.

Examples of the alkoxyalkyl group in R^(a33) include a methoxymethylgroup, an ethoxyethyl group, a propoxymethyl group, an isopropoxymethylgroup, a butoxymethyl group, a sec-butoxymethyl group and atert-butoxymethyl group. The alkoxyalkyl group is preferably analkoxyalkyl group having 2 to 8 carbon atoms, more preferably amethoxymethyl group or an ethoxyethyl group, and still more preferably amethoxymethyl group.

Examples of the alkoxyalkoxy group in R^(a33) include a methoxymethoxygroup, a methoxyethoxy group, an ethoxymethoxy group, an ethoxyethoxygroup, a propoxymethoxy group, an isopropoxymethoxy group, abutoxymethoxy group, a sec-butoxymethoxy group and a tert-butoxymethoxygroup. The alkoxyalkoxy group is preferably an alkoxyalkoxy group having2 to 8 carbon atoms, and more preferably a methoxyethyl group or anethoxyethyl group.

Examples of the alkylcarbonyl group in R^(a33) include an acetyl group,a propionyl group and a butyryl group. The alkylcarbonyl group ispreferably an alkylcarbonyl group having 2 to 3 carbon atoms, and morepreferably an acetyl group.

Examples of the alkylcarbonyloxy group in R^(a33) include an acetyloxygroup, a propionyloxy group and a butyryloxy group. The alkylcarbonyloxygroup is preferably an alkylcarbonyloxy group having 2 to 3 carbonatoms, and more preferably an acetyloxy group.

R^(a33) is preferably a halogen atom, a hydroxy group, an alkyl grouphaving 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atomsor an alkoxyalkoxy group having 2 to 8 carbon atoms, more preferably afluorine atom, an iodine atom, a hydroxy group, a methyl group, amethoxy group, an ethoxy group, an ethoxyethoxy group or anethoxymethoxy group, and still more preferably a fluorine atom, aniodine atom, a hydroxy group, a methyl group, a methoxy group or anethoxyethoxy group.

Examples of the *—X^(a31)-(A^(a32)-X^(a32))_(nc)— include *—O—, *—CO—O—,*—O—CO—, *—CO—O-A^(a32)-CO—O—, *—O—CO-A^(a32)-O—, *—O-A^(a32)-CO—O—,*—CO—O-A^(a32)-O—CO— and *—O—CO-A^(a32)-O—CO. Of these, *—CO—O—,*—CO—O-A^(a32)-CO—O— or *—O-A^(a32)-CO—O— is preferable.

Examples of the alkanediyl group include a methylene group, an ethylenegroup, a propane-1,3-diyl group, a propane-1,2-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diylgroup, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a2-methylbutane-1,4-diyl group.

A^(a32) is preferably a methylene group or an ethylene group.

A^(a30) is preferably a single bond, *—CO—O— or *—CO—O-A^(a32)-CO—O—,more preferably a single bond, *—CO—O— or *—CO—O—CH₂—CO—O—, and stillmore preferably a single bond or *—CO—O—.

la is preferably 0, 1 or 2, more preferably 0 or 1, and still morepreferably 0.

Examples of the hydrocarbon group in R^(a34), R^(a35) and R^(a36)include an alkyl group, an alicyclic hydrocarbon group, an aromatichydrocarbon group, and groups formed by combining these groups.

Examples of the alkyl group include a methyl group, an ethyl group, apropyl group, a butyl group, a pentyl group, a hexyl group, a heptylgroup, an octyl group and the like.

The alicyclic hydrocarbon group may be either monocyclic or polycyclic.Examples of the monocyclic alicyclic hydrocarbon group includecycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, acycloheptyl group and a cyclooctyl group. Examples of the polycyclicalicyclic hydrocarbon group include a decahydronaphthyl group, anadamantyl group, a norbornyl group and the following groups (*represents a bonding site).

Examples of the aromatic hydrocarbon group include aryl groups such as aphenyl group, a naphthyl group, an anthryl group, a biphenyl group and aphenanthryl group.

Examples of the combined group include groups obtained by combining theabove-mentioned alkyl group and alicyclic hydrocarbon group (e.g.,alkylcycloalkyl groups or cycloalkylalkyl groups such asmethylcyclohexyl groups, dimethylcyclohexyl groups, methylnorbornylgroups, cyclohexylmethyl groups, adamantylmethyl groups,adamantyldimethyl groups, and norbornylethyl groups), aralkyl groupssuch as a benzyl group, aromatic hydrocarbon groups having an alkylgroup (a p-methylphenyl group, a p-tert-butylphenyl group, a tolylgroup, a xylyl group, a cumenyl group, a mesityl group, a2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group, etc.), aromatichydrocarbon groups having an alicyclic hydrocarbon group (ap-cyclohexylphenyl group, a p-adamantylphenyl group, etc.),aryl-cycloalkyl groups such as a phenylcyclohexyl group and the like.Particularly, examples of R^(a36) include an alkyl group having 1 to 18carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbonatoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or agroup formed by combining these groups.

R^(a34) is preferably a hydrogen atom.

R^(a35) is preferably a hydrogen atom, an alkyl group having 1 to 12carbon atoms or an alicyclic hydrocarbon group having 3 to 12 carbonatoms, and more preferably a methyl group or an ethyl group.

The hydrocarbon group of R^(a36) is preferably an alkyl group having 1to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbonatoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or agroup formed by combining these groups, and more preferably an alkylgroup having 1 to 18 carbon atoms, an alicyclic aliphatic hydrocarbongroup having 3 to 18 carbon atoms or an aralkyl group having 7 to 18carbon atoms. The alkyl group and the alicyclic hydrocarbon group inR^(a36) are preferably unsubstituted. The aromatic hydrocarbon group inR^(a36) is preferably an aromatic ring having an aryloxy group having 6to 10 carbon atoms.

—OC(R^(a34))(R^(a33))—O—R^(a36) in the structural unit (a1-4) iseliminated by contacting with an acid (e.g., p-toluenesulfonic acid) toform a hydroxy group.

—OC(R^(a34))(R^(a33))—O—R^(a36) is preferably bonded to theortho-position or the para-position of the benzene ring, and morepreferably the para-position.

The structural unit (a1-4) includes, for example, structural unitsderived from the monomers mentioned in JP 2010-204646 A. The structuralunit preferably includes structural units represented by formula(a1-4-1) to formula (a1-4-18) and a structural unit in which a hydrogenatom corresponding to R^(a32) is substituted with a methyl group, andmore preferably structural units represented by formula (a1-4-1) toformula (a1-4-5), formula (a1-4-10), formula (a1-4-13) and formula(a1-4-14).

When the resin (A) includes the structural unit (a1-4), the content ispreferably 3 to 80 mol %, more preferably 5 to 75 mol %, still morepreferably 7 to 70 mol %, yet more preferably 7 to 65 mol %, andparticularly preferably 10 to 60 mol %, based on the total of allstructural units of the resin (A).

The structural unit derived from a (meth)acrylic monomer having a group(2) also includes a structural unit represented by formula (a1-5)(hereinafter sometimes referred to as “structural unit (a1-5)”).

In formula (a1-5),

R^(a8) represents an alkyl group having 1 to 6 carbon atoms which mayhave a halogen atom, a hydrogen atom or a halogen atom,

Z^(a1) represents a single bond or *—(CH₂)_(h3)—CO-L⁵⁴-, h3 representsan integer of 1 to 4, and * represents a bonding site to L⁵¹,

L⁵¹, L⁵², L⁵³ and L⁵⁴ each independently represent —O— or —S—,

s1 represents an integer of 1 to 3, and

s1′ represents an integer of 0 to 3.

The halogen atom includes a fluorine atom and a chlorine atom and ispreferably a fluorine atom. Examples of the alkyl group having 1 to 6carbon atoms which may have a halogen atom include a methyl group, anethyl group, a propyl group, a butyl group, a pentyl group, a hexylgroup, a heptyl group, an octyl group, a fluoromethyl group and atrifluoromethyl group.

In formula (a1-5), R^(a8) is preferably a hydrogen atom, a methyl groupor a trifluoromethyl group,

L⁵¹ is preferably an oxygen atom,

one of L⁵² and L⁵³ is preferably —O— and the other one is preferably—S—,

s1 is preferably 1,

s1′ is preferably an integer of 0 to 2, and

Z^(a1) is preferably a single bond or *—CH₂—CO—O—.

The structural unit (a1-5) includes, for example, structural unitsderived from the monomers mentioned in JP 2010-61117 A. Of thesestructural units, structural units represented by formula (a1-5-1) toformula (a1-5-4) are preferable, and structural units represented byformula (a1-5-1) or formula (a1-5-2) are more preferable.

When the resin (A) includes the structural unit (a1-5), the content ispreferably 1 to 50 mol %, more preferably 3 to 45 mol %, still morepreferably 5 to 40 mol %, and yet more preferably 5 to 30 mol %, basedon all structural units of the resin (A).

The structural unit (a1) also includes the following structural units.

When the resin (A) includes the above-mentioned structural units such as(a1-3-1) to (a1-3-7), the content is preferably 10 to 95 mol %, morepreferably 15 to 90 mol %, still more preferably 20 to 85 mol %, yetmore preferably 20 to 70 mol %, and particularly preferably 20 to 60 mol%, based on all structural units of the resin (A).

The structural unit (a1) also includes the following structural units.

When the resin (A) includes the above-mentioned structural units such as(a1-6-1) to (a1-6-3), the content is preferably 10 to 60 mol %, morepreferably 15 to 55 mol %, still more preferably 20 to 50 mol %, yetmore preferably 20 to 45 mol %, and particularly preferably 20 to 40 mol%, based on all structural units of the resin (A).

<Structural Unit (s)>

The structural unit (s) is derived from a monomer having no acid-labilegroup (hereinafter sometimes referred to as “monomer (s)”). It ispossible to use, as the monomer from which the structural unit (s) isderived, a monomer having no acid-labile group known in the resistfield.

The structural unit (s) preferably has a hydroxy group or a lactonering. When a resin including a structural unit having a hydroxy groupand having no acid-labile group (hereinafter sometimes referred to as“structural unit (a2)”) and/or a structural unit having a lactone ringand having no acid-labile group (hereinafter sometimes referred to as“structural unit (a3)”) is used in the resist composition according tosome embodiments of the present disclosure, it is possible to improvethe resolution of a resist pattern and the adhesion to a substrate.

<Structural Unit (a2)>

The hydroxy group possessed by the structural unit (a2) may be either analcoholic hydroxy group or a phenolic hydroxy group.

When a resist pattern is produced from the resist composition accordingto some embodiments of the present disclosure, in the case of using, asan exposure source, high energy rays such as KrF excimer laser (248 nm),electron beam or extreme ultraviolet light (EUV), a structural unit (a2)having a phenolic hydroxy group is preferably used as the structuralunit (a2), and the below-mentioned structural unit (a2-A) is morepreferably used. When using ArF excimer laser (193 nm) or the like, astructural unit (a2) having an alcoholic hydroxy group is preferablyused as the structural unit (a2), and it is more preferably to use astructural unit (a2-1) mentioned later. The structural unit (a2) may beincluded alone, or two or more structural units may be included.

In the structural unit (a2), examples of the structural unit having aphenolic hydroxy group include a structural unit represented by formula(a2-A) (hereinafter sometimes referred to as “structural unit (a2-A)”).

wherein, in formula (a2-A),

R^(a50) represents a hydrogen atom, a halogen atom or an alkyl grouphaving 1 to 6 carbon atoms which may have a halogen atom,

R^(a51) represents a halogen atom, a hydroxy group, an alkyl grouphaving 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms,an alkoxyalkyl group having 2 to 12 carbon atoms, an alkoxyalkoxy grouphaving 2 to 12 carbon atoms, an alkylcarbonyl group having 2 to 4 carbonatoms, an alkylcarbonyloxy group having 2 to 4 carbon atoms, anacryloyloxy group or a methacryloyloxy group,

A^(a50) represents a single bond or *—X^(a51)-(A^(a52)-X^(a52))_(nb)—and * represents a bonding site to carbon atoms to which —R^(a50) isbonded,

A^(a52) represents an alkanediyl group having 1 to 6 carbon atoms,

X^(a51) and X^(a52) each independently represent —O—, —CO—O— or —O—CO—,

nb represents 0 or 1, and

mb represents an integer of 0 to 4, and when mb is an integer of 2 ormore, a plurality of R^(a51) may be the same or different from eachother.

Examples of the halogen atom in R^(a50) and R^(a51) include a fluorineatom, a chlorine atom and a bromine atom.

Examples of the alkyl group having 1 to 6 carbon atoms which may have ahalogen atom in R^(a50) include a trifluoromethyl group, adifluoromethyl group, a methyl group, a perfluoroethyl group, a2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethylgroup, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, apropyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutylgroup, a butyl group, a perfluoropentyl group, a2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl groupand a perfluorohexyl group.

R^(a50) is preferably a hydrogen atom or an alkyl group having 1 to 4carbon atoms, more preferably a hydrogen atom, a methyl group or anethyl group, and still more preferably a hydrogen atom or a methylgroup.

Examples of the alkyl group in R^(a51) include a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, a sec-butylgroup, a tert-butyl group, a pentyl group and a hexyl group. The alkylgroup is preferably an alkyl group having 1 to 4 carbon atoms, morepreferably a methyl group or an ethyl group, and still more preferably amethyl group.

Examples of the alkoxy group in R^(a51) include a methoxy group, anethoxy group, a propoxy group, an isopropoxy group, a butoxy group, asec-butoxy group and a tert-butoxy group. The alkoxy group is preferablyan alkoxy group having 1 to 4 carbon atoms, more preferably a methoxygroup or an ethoxy group, and still more preferably a methoxy group.

Examples of the alkoxyalkyl group in R^(a51) include a methoxymethylgroup, an ethoxyethyl group, a propoxymethyl group, an isopropoxymethylgroup, a butoxymethyl group, a sec-butoxymethyl group and atert-butoxymethyl group. The alkoxyalkyl group is preferably analkoxyalkyl group having 2 to 8 carbon atoms, more preferably amethoxymethyl group or an ethoxyethyl group, and still more preferably amethoxymethyl group.

Examples of the alkoxyalkoxy group in R^(a51) include a methoxymethoxygroup, a methoxyethoxy group, an ethoxymethoxy group, an ethoxyethoxygroup, a propoxymethoxy group, an isopropoxymethoxy group, abutoxymethoxy group, a sec-butoxymethoxy group and a tert-butoxymethoxygroup. The alkoxyalkoxy group is preferably an alkoxyalkoxy group having2 to 8 carbon atoms, and more preferably a methoxyethoxy group or anethoxyethoxy group.

Examples of the alkylcarbonyl group in R^(a51) include an acetyl group,a propionyl group and a butyryl group. The alkylcarbonyl group ispreferably an alkylcarbonyl group having 2 to 3 carbon atoms, and morepreferably an acetyl group.

Examples of the alkylcarbonyloxy group in R^(a51) include an acetyloxygroup, a propionyloxy group and a butyryloxy group. The alkylcarbonyloxygroup is preferably an alkylcarbonyloxy group having 2 to 3 carbonatoms, and more preferably an acetyloxy group.

R^(a51) is preferably a halogen atom, a hydroxy group, an alkyl grouphaving 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atomsor an alkoxyalkoxy group having 2 to 8 carbon atoms, more preferably afluorine atom, an iodine atom, a hydroxy group, a methyl group, amethoxy group, an ethoxy group, an ethoxyethoxy group or anethoxymethoxy group, and still more preferably a fluorine atom, aniodine atom, a hydroxy group, a methyl group, a methoxy group or anethoxyethoxy group.

Examples of *—X^(a51)-(A^(a52)-X^(a52))_(nb)— include *—O—, *—CO—,*—O—CO—, *—CO—O-A^(a52)-CO—O—, *—O—CO-A^(a52)-, *—O-A^(a52)-CO—O—,*—CO—O-A^(a52)-O—CO— and *—O—CO-A^(a52)-O—CO—. Of these, *—CO—O—,*—CO—O-A^(a52)-CO—O— or *—O-A^(a52)-CO—O— is preferable.

Examples of the alkanediyl group include a methylene group, an ethylenegroup, a propane-1,3-diyl group, a propane-1,2-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diylgroup, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a2-methylbutane-1,4-diyl group.

A^(a52) is preferably a methylene group or an ethylene group.

A^(a50) is preferably a single bond, *—CO—O— or *—CO—O-A^(a52)-CO—O—,more preferably a single bond, *—CO—O— or *—CO—O—CH₂—CO—O—, and stillmore preferably a single bond or *—CO—O—

mb is preferably 0, 1 or 2, more preferably 0 or 1, and still morepreferably 0.

The hydroxy group is preferably bonded to the o-position or thep-position of a benzene ring, and more preferably the p-position.

Examples of the structural unit (a2-A) include structural units derivedfrom the monomers mentioned in JP 2010-204634 A and JP 2012-12577 A.

Examples of the structural unit (a2-A) include structural unitsrepresented by formula (a2-2-1) to formula (a2-2-16), and a structuralunit in which a methyl group corresponding to R^(a50) in the structuralunit (a2-A) is substituted with a hydrogen atom in structural unitsrepresented by formula (a2-2-1) to formula (a2-2-16). The structuralunit (a2-A) is preferably a structural unit represented by formula(a2-2-1), a structural unit represented formula (a2-2-3), a structuralunit represented by formula (a2-2-6), a structural unit represented byformula (a2-2-8), structural units represented by formula (a2-2-12) toformula (a2-2-14), and structural units in which a methyl groupcorresponding to R^(a50) in the structural unit (a2-A) is substitutedwith a hydrogen atom in a structural unit represented by formula(a2-2-1), a structural unit represented by formula (a2-2-3), astructural unit represented by formula (a2-2-6), a structural unitrepresented by formula (a2-2-8) and structural units represented byformula (a2-2-12) to formula (a2-2-14), more preferably a structuralunit represented by formula (a2-2-3), a structural unit represented byformula (a2-2-8), structural units represented by formula (a2-2-12) toformula (a2-2-14), and structural units in which a methyl groupcorresponding to R^(a50) in the structural unit (a2-A) is substitutedwith a hydrogen atom in a structural unit represented by formula(a2-2-3) or a structural unit represented by formula (a2-2-8) orstructural units represented by formula (a2-2-12) to formula (a2-2-14),and still more preferably a structural unit represented by formula(a2-2-8) and a structural unit in which a methyl group corresponding toR^(a50) in the structural unit (a2-A) is substituted with a hydrogenatom in a structural unit represented by formula (a2-2-8).

When the structural unit (a2-A) is included in the resin (A), thecontent of the structural unit (a2-A) is preferably 5 to 80 mol %, morepreferably 10 to 70 mol %, still more preferably 15 to 65 mol %, and yetmore preferably 20 to 65 mol %, based on all structural units.

The structural unit (a2-A) can be included in a resin (A) bypolymerizing, for example, with a structural unit (a1-4) and treatingwith an acid such as p-toluenesulfonic acid. The structural unit (a2-A)can also be included in the resin (A) by polymerizing withacetoxystyrene and treating with an alkali such as tetramethylammoniumhydroxide.

Examples of the structural unit having an alcoholic hydroxy group in thestructural unit (a2) include a structural unit represented by formula(a2-1) (hereinafter sometimes referred to as “structural unit (a2-1)”).

In formula (a2-1),

L^(a3) represents —O— or *—O—(CH₂)_(k2)—CO—O—,

k2 represents an integer of 1 to 7, and * represents a bonding site to—CO—,

R^(a14) represents a hydrogen atom or a methyl group,

R^(a15) and R^(a16) each independently represent a hydrogen atom, amethyl group or a hydroxy group, and

o1 represents an integer of 0 to 10.

In formula (a2-1), L^(a3) is preferably —O— or —O—(CH₂)_(f1)—CO—O— (f1represents an integer of 1 to 4), and more preferably —O—,

R^(a14) is preferably a methyl group,

R^(a15) is preferably a hydrogen atom,

R^(a16) is preferably a hydrogen atom or a hydroxy group, and

o1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

The structural unit (a2-1) includes, for example, structural unitsderived from the monomers mentioned in JP 2010-204646 A. A structuralunit represented by any one of formula (a2-1-1) to formula (a2-1-6) ispreferable, a structural unit represented by any one of formula (a2-1-1)to formula (a2-1-4) is more preferable, and a structural unitrepresented by formula (a2-1-1) or formula (a2-1-3) is still morepreferable.

When the resin (A) includes the structural unit (a2-1), the content isusually 1 to 45 mol %, preferably 1 to 40 mol %, more preferably 1 to 35mol %, still more preferably 1 to 20 mol %, and yet more preferably 1 to10 mol %, based on all structural units of the resin (A).

<Structural Unit (a3)>

The lactone ring possessed by the structural unit (a3) may be amonocyclic ring such as a β-propiolactone ring, a γ-butyrolactone ringor a δ-valerolactone ring, or a condensed ring of a monocyclic lactonering and the other ring. Preferably, a γ-butyrolactone ring, anadamantanelactone ring or a bridged ring including a γ-butyrolactonering structure (e.g. a structural unit represented by the followingformula (a3-2)) is exemplified.

The structural unit (a3) is preferably a structural unit represented byformula (a3-1), formula (a3-2), formula (a3-3) or formula (a3-4). Thesestructural units may be included alone, or two or more structural unitsmay be included:

wherein, in formula (a3-1), formula (a3-2), formula (a3-3) and formula(a3-4),

L^(a4), L^(a5) and L^(a6) each independently represent —O— or a grouprepresented by *—O—(CH₂)_(k3)—CO—O— (k3 represents an integer of 1 to7),

L^(a7) represents —O—, *—O-L^(a8)-O—, *—O-L^(a8)-CO—O—,*—O-L^(a8)-CO—O-L^(a9)-CO—O— or *—O-L^(a8)-O—CO-L^(a9)_O,

L^(a8) and L^(a9) each independently represent an alkanediyl grouphaving 1 to 6 carbon atoms,

* represents a bonding site to a carbonyl group,

R^(a18), R^(a19) and R^(a20) each independently represent a hydrogenatom or a methyl group,

R^(a24) represents an alkyl group having 1 to 6 carbon atoms which mayhave a halogen atom, a hydrogen atom or a halogen atom,

X^(a3) represents —CH₂— or an oxygen atom,

R^(a21) represents an aliphatic hydrocarbon group having 1 to 4 carbonatoms,

R^(a22), R^(a23) and R^(a25) each independently represent a carboxygroup, a cyano group or an aliphatic hydrocarbon group having 1 to 4carbon atoms,

p1 represents an integer of 0 to 5,

q1 represents an integer of 0 to 3,

r1 represents an integer of 0 to 3,

w1 represents an integer of 0 to 8, and

when p1, q1, r1 and/or w1 is/are 2 or more, a plurality of R^(a21),R^(a22), R^(a23) and/or R^(a25) may be the same or different from eachother.

Examples of the aliphatic hydrocarbon group in R^(a21), R^(a22), R^(a23)and R^(a25) include alkyl groups such as a methyl group, an ethyl group,a propyl group, an isopropyl group, a butyl group, a sec-butyl group anda tert-butyl group.

Examples of the halogen atom in R^(a24) include a fluorine atom, achlorine atom, a bromine atom and an iodine atom.

Examples of the alkyl group in R^(a24) include a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, a sec-butylgroup, a tert-butyl group, a pentyl group and a hexyl group, and thealkyl group is preferably an alkyl group having 1 to 4 carbon atoms, andmore preferably a methyl group or an ethyl group.

Examples of the alkyl group having a halogen atom in R^(a24) include atrifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group,a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butylgroup, a perfluorotert-butyl group, a perfluoropentyl group, aperfluorohexyl group, a trichloromethyl group, a tribromomethyl group, atriiodomethyl group and the like.

Examples of the alkanediyl group in Las and L^(a9) include a methylenegroup, an ethylene group, a propane-1,3-diyl group, a propane-1,2-diylgroup, a butane-1,4-diyl group, a pentane-1,5-diyl group, ahexane-1,6-diyl group, a butane-1,3-diyl group, a2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, apentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group.

In formula (a3-1) to formula (a3-3), preferably, L^(a4) to L^(a6) areeach independently —O— or a group in which k3 is an integer of 1 to 4 in*—O—(CH₂)_(k3)—CO—O—, more preferably —O— and *—O—CH₂—CO—O—, and stillmore preferably an oxygen atom,

R^(a18) to R^(a21) are preferably a methyl group,

preferably, R^(a22) and R^(a23) are each independently a carboxy group,a cyano group or a methyl group, and

preferably, p1, q1 and r1 are each independently an integer of 0 to 2,and more preferably 0 or 1.

In formula (a3-4), R^(a24) is preferably a hydrogen atom or an alkylgroup having 1 to 4 carbon atoms, more preferably a hydrogen atom, amethyl group or an ethyl group, and still more preferably a hydrogenatom or a methyl group,

R^(a25) is preferably a carboxy group, a cyano group or a methyl group,

L^(a7) is preferably —O— or *—O-L^(a8)-CO—O—, and more preferably —O—,—O—CH₂—CO—O— or —O—C₂H₄—CO—O—, and

w1 is preferably an integer of 0 to 2, and more preferably 0 or 1.

Particularly, formula (a3-4) is preferably formula (a3-4)′:

wherein R^(a24) and L^(a7) are the same as defined above.

Examples of the structural unit (a3) include structural units derivedfrom the monomers mentioned in JP 2010-204646 A, the monomers mentionedin JP 2000-122294 A and the monomers mentioned in JP 2012-41274 A. Thestructural unit (a3) is preferably a structural unit represented by anyone of formula (a3-1-1), formula (a3-1-2), formula (a3-2-1), formula(a3-2-2), formula (a3-3-1), formula (a3-3-2) and formula (a3-4-1) toformula (a3-4-12), and structural units in which methyl groupscorresponding to R^(a18), R^(a19), R^(a20) and R^(a24) in formula (a3-1)to formula (a3-4) are substituted with hydrogen atoms in the abovestructural units.

When the resin (A) includes the structural unit (a3), the total contentis usually 5 to 70 mol %, preferably 10 to 65 mol %, and more preferably10 to 60 mol %, based on all 5 structural units of the resin (A).

Each content of the structural unit (a3-1), the structural unit (a3-2),the structural unit (a3-3) or the structural unit (a3-4) is preferably 5to 60 mol, more preferably 5 to 50 mol %, and still more preferably 10to 50 mol %, based on all structural units of the resin (A).

<Structural Unit (a4)>

Examples of the structural unit (a4) include the following structuralunits:

wherein, in formula (a4),

R⁴¹ represents a hydrogen atom or a methyl group, and

R⁴² represents a saturated hydrocarbon group having 1 to 24 carbon atomswhich has a halogen atom, and —CH₂— included in the saturatedhydrocarbon group may be replaced by —O— or —CO—.

Examples of the saturated hydrocarbon group represented by R⁴² include achain saturated hydrocarbon group and a monocyclic or polycyclicalicyclic saturated hydrocarbon group, and groups formed by combiningthese groups.

Examples of the chain saturated hydrocarbon group include a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a decyl group, a dodecylgroup, a pentadecyl group, a hexadecyl group, a heptadecyl group and anoctadecyl group.

Examples of the monocyclic or polycyclic alicyclic saturated hydrocarbongroup include cycloalkyl groups such as a cyclopentyl group, acyclohexyl group, a cycloheptyl group and a cyclooctyl group; andpolycyclic alicyclic saturated hydrocarbon groups such as adecahydronaphthyl group, an adamantyl group, a norbornyl group and thefollowing groups (* represents a bonding site).

Examples of the group formed by combination include groups formed bycombining one or more alkyl groups or one or more alkanediyl groups withone or more alicyclic saturated hydrocarbon groups, and include analkanediyl group-alicyclic saturated hydrocarbon group, an alicyclicsaturated hydrocarbon group-alkyl group, an alkanediyl group-alicyclicsaturated hydrocarbon group-alkyl group and the like.

Examples of the structural unit (a4) include a structural unitrepresented by formula (a4-0), a structural unit represented by formula(a4-1) and a structural unit represented by formula (a4-4):

wherein, in formula (a4-0),

R⁵⁴ represents a hydrogen atom or a methyl group,

L^(4a) represents a single bond or an alkanediyl group having 1 to 4carbon atoms,

L^(3a) represents a perfluoroalkanediyl group having 1 to 8 carbon atomsor a perfluorocycloalkanediyl group having 3 to 12 carbon atoms, and

R⁶⁴ represents a hydrogen atom or a fluorine atom.

Examples of the alkanediyl group in L^(4a) include linear alkanediylgroups such as a methylene group, an ethylene group, a propane-1,3-diylgroup and a butane-1,4-diyl group; and branched alkanediyl groups suchas an ethane-1,1-diyl group, a propane-1,2-diyl group, a butane-1,3-diylgroup, a 2-methylpropane-1,3-diyl group and a 2-methylpropane-1,2-diylgroup.

Examples of the perfluoroalkanediyl group in L^(3a) include adifluoromethylene group, a perfluoroethylene group, aperfluoroethylfluoromethylene group, a perfluoropropane-1,3-diyl group,a perfluoropropane-1,2-diyl group, a perfluoropropane-2,2-diyl group, aperfluorobutane-1,4-diyl group, a perfluorobutane-2,2-diyl group, aperfluorobutane-1,2-diyl group, a perfluoropentane-1,5-diyl group, aperfluoropentane-2,2-diyl group, a perfluoropentane-3,3-diyl group, aperfluorohexane-1,6-diyl group, a perfluorohexane-2,2-diyl group, aperfluorohexane-3,3-diyl group, a perfluoroheptane-1,7-diyl group, aperfluoroheptane-2,2-diyl group, a perfluoroheptane-3,4-diyl group, aperfluoroheptane-4,4-diyl group, a perfluorooctane-1,8-diyl group, aperfluorooctane-2,2-diyl group, a perfluorooctane-3,3-diyl group, aperfluorooctane-4,4-diyl group and the like.

Examples of the perfluorocycloalkanediyl group in L^(3a) include aperfluorocyclohexanediyl group, a perfluorocyclopentanediyl group, aperfluorocycloheptanediyl group, a perfluoroadamantanediyl group and thelike.

L^(4a) is preferably a single bond, a methylene group or an ethylenegroup, and more preferably a single bond or a methylene group.

L^(3a) is preferably a perfluoroalkanediyl group having 1 to 6 carbonatoms, and more preferably a perfluoroalkanediyl group having 1 to 3carbon atoms.

Examples of the structural unit (a4-0) include the following structuralunits, and structural units in which a methyl group corresponding to R⁵⁴in the structural unit (a4-0) in the following structural units issubstituted with a hydrogen atom:

wherein, in formula (a4-1),

R^(a41) represents a hydrogen atom or a methyl group,

R^(a42) represents a hydrocarbon group having 1 to 20 carbon atoms whichmay have a substituent, and —CH₂— included in the saturated hydrocarbongroup may be replaced by —O— or —CO—,

A^(a41) represents an alkanediyl group having 1 to 6 carbon atoms whichmay have a substituent or a group represented by formula (a-g1), inwhich at least one of A^(a41) and R^(a42) has, as a substituent, ahalogen atom (preferably a fluorine atom):

[in which, in formula (a-g1),

s represents 0 or 1,

A^(a42) and A^(a44) each independently represent a divalent saturatedhydrocarbon group having 1 to 5 carbon atoms which may have asubstituent,

A^(a43) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 5 carbon atoms which may have a substituent,

X^(a41) and X^(a42) each independently represent —O—, —CO—, —CO—O— or—O—CO—, in which the total number of carbon atoms of A^(a42), A^(a43),A^(a44), X^(a41) and X^(a42) is 7 or less], and

* represents a bonding site and * at the right side represents a bondingsite to —O—CO—R^(a42).

Examples of the saturated hydrocarbon group in R^(a42) include a chainhydrocarbon group and a monocyclic or polycyclic saturated alicyclichydrocarbon group, and groups formed by combining these groups.

Examples of the chain hydrocarbon group include a methyl group, an ethylgroup, a propyl group, a butyl group, a pentyl group, a hexyl group, aheptyl group, an octyl group, a decyl group, a dodecyl group, apentadecyl group, a hexadecyl group, a heptadecyl group and an octadecylgroup.

Examples of the monocyclic or polycyclic saturated alicyclic hydrocarbongroup include cycloalkyl groups such as a cyclopentyl group, acyclohexyl group, a cycloheptyl group and a cyclooctyl group; andpolycyclic alicyclic hydrocarbon groups such as a decahydronaphthylgroup, an adamantyl group, a norbornyl group and the following groups (*represents a bonding site).

Examples of the group formed by combination include groups formed bycombining one or more alkyl groups or one or more alkanediyl groups withone or more saturated alicyclic hydrocarbon groups, and include analkanediyl group-saturated alicyclic hydrocarbon group, a saturatedalicyclic hydrocarbon group-alkyl group, an alkanediyl group-saturatedalicyclic hydrocarbon group-alkyl group and the like.

Examples of the substituent possessed by R^(a42) include at least oneselected from the group consisting of a halogen atom and the groupconsisting of the group represented by formula (a-g3). Examples of thehalogen atom include a fluorine atom, a chlorine atom, a bromine atomand an iodine atom, and a fluorine atom is preferable:*-a43-A^(a45)  (a.g3)wherein, in formula (a-g3),

X^(a43) represents an oxygen atom, a carbonyl group, *—O—CO— or *—CO—O—,

A^(a45) represents a saturated hydrocarbon group having 1 to 17 carbonatoms which may have a halogen atom, and

* represents a bonding site to R^(a42).

In R^(a42)—X^(a43)-A^(a43), when R^(a42) has no halogen atom, A^(a45)represents a saturated hydrocarbon group having 1 to 17 carbon atomshaving at least one halogen atom.

Examples of the saturated hydrocarbon group in A^(a45) include alkylgroups such as a methyl group, an ethyl group, a propyl group, a butylgroup, a pentyl group, a hexyl group, a heptyl group, an octyl group, adecyl group, a dodecyl group, a pentadecyl group, a hexadecyl group, aheptadecyl group and an octadecyl group; monocyclic alicyclichydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, acycloheptyl group and a cyclooctyl group; and polycyclic alicyclichydrocarbon groups such as a decahydronaphthyl group, an adamantylgroup, a norbornyl group and the following groups (* represents abonding site).

Examples of the group formed by combination include a group obtained bycombining one or more alkyl groups or one or more alkanediyl groups withone or more alicyclic hydrocarbon groups, and include an -alkanediylgroup-alicyclic hydrocarbon group, an -alicyclic hydrocarbon group-alkylgroup, an -alkanediyl group-alicyclic hydrocarbon group-alkyl group andthe like.

R^(a42) is preferably a saturated hydrocarbon group which may have ahalogen atom, and more preferably an alkyl group having a halogen atomand/or a saturated hydrocarbon group having a group represented byformula (a-g3).

When R^(a42) is a saturated hydrocarbon group having a halogen atom, asaturated hydrocarbon group having a fluorine atom is preferable, aperfluoroalkyl group or a perfluorocycloalkyl group is more preferable,a perfluoroalkyl group having 1 to 6 carbon atoms is still morepreferable, and a perfluoroalkyl group having 1 to 3 carbon atoms isparticularly preferable. Examples of the perfluoroalkyl group include aperfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group,a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group,a perfluoroheptyl group and a perfluorooctyl group. Examples of theperfluorocycloalkyl group include a perfluorocyclohexyl group and thelike.

When R^(a42) is a saturated hydrocarbon group having a group representedby formula (a-g3), the total number of carbon atoms of R^(a42) ispreferably 15 or less, and more preferably 12 or less, including thenumber of carbon atoms included in the group represented by formula(a-g3). When having the group represented by formula (a-g3) as thesubstituent, the number thereof is preferably 1.

When R^(a42) is a saturated hydrocarbon group having the grouprepresented by formula (a-g3), R^(a42) is still more preferably a grouprepresented by formula (a-g2):*-A^(a46)-X^(a44)-A^(a47)  (a-g2)wherein, in formula (a-g2),

A^(a46) represents a divalent saturated hydrocarbon group having 1 to 17carbon atoms which may have a halogen atom,

X^(a44) represents **—O—CO— or **—CO—O— (** represents a bonding site toA^(a46)),

A^(a47) represents a saturated hydrocarbon group having 1 to 17 carbonatoms which may have a halogen atom,

the total number of carbon atoms of A^(a46), A^(a47) and X^(a44) is 18or less, and at least one of A^(a46) and A^(a47) has at least onehalogen atom, and

* represents a bonding site to a carbonyl group.

The number of carbon atoms of the saturated hydrocarbon group of A^(a46)is preferably 1 to 6, and more preferably 1 to 3.

The number of carbon atoms of the saturated hydrocarbon group of A^(a47)is preferably 4 to 15, and more preferably 5 to 12, and A^(a47) is stillmore preferably a cyclohexyl group or an adamantyl group.

Preferred structure of the group represented by formula (a-g2) is thefollowing structure (* represents a bonding site to a carbonyl group).

Examples of the alkanediyl group in A^(a41) include linear alkanediylgroups such as a methylene group, an ethylene group, a propane-1,3-diylgroup, a butane-1,4-diyl group, a pentane-1,5-diyl group and ahexane-1,6-diyl group; and branched alkanediyl groups such as apropane-1,2-diyl group, a butane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a 1-methylbutane-1,4-diyl group and a2-methylbutane-1,4-diyl group.

Examples of the substituent in the alkanediyl group represented byA^(a41) include a hydroxy group and an alkoxy group having 1 to 6 carbonatoms.

A^(a41) is preferably an alkanediyl group having 1 to 4 carbon atoms,more preferably an alkanediyl group having 2 to 4 carbon atoms, andstill more preferably an ethylene group.

Examples of the divalent saturated hydrocarbon group represented byA^(a42), A^(a43) and A^(a44) in the group represented by formula (a-g1)include a linear or branched alkanediyl group and a monocyclic divalentalicyclic saturated hydrocarbon group, and divalent saturatedhydrocarbon groups formed by combining an alkanediyl group and adivalent alicyclic saturated hydrocarbon group. Specific examplesthereof include a methylene group, an ethylene group, a propane-1,3-diylgroup, a propane-1,2-diyl group, a butane-1,4-diyl group, a1-methylpropane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group and the like.

Examples of the substituent of the divalent saturated hydrocarbon grouprepresented by A^(a42), A^(a43) and A^(a44) include a hydroxy group andan alkoxy group having 1 to 6 carbon atoms.

s is preferably 0.

In the group represented by formula (a-g1), examples of the group inwhich X^(a42) is —O—, —CO—, —CO—O— or —O—CO— include the followinggroups. In the following exemplification, * and ** each represent aboning site, and ** represents a boning site to —O—CO—R^(a42).

Examples of the structural unit represented by formula (a4-1) includethe following structural units, and structural units in which a methylgroup corresponding to A^(a41) in the structural unit represented byformula (a4-1) in the following structural units is substituted with ahydrogen atom.

Examples of the structural unit represented by formula (a4-1) include astructural unit represented by formula (a4-2) and a structural unitrepresented by formula (a4-3):

wherein, in formula (a4-2),

R^(f5) represents a hydrogen atom or a methyl group,

L⁴⁴ represents an alkanediyl group having 1 to 6 carbon atoms, and —CH₂—included in the alkanediyl group may be replaced by —O— or —CO—,

R^(f6) represents a saturated hydrocarbon group having 1 to 20 carbonatoms having a fluorine atom, and

the upper limit of the total number of carbon atoms of L⁴⁴ and R^(f6) is21.

Examples of the alkanediyl group having 1 to 6 carbon atoms of L⁴⁴include the same groups as mentioned for A^(a41).

Examples of the saturated hydrocarbon group of R^(f6) include the samegroups as mentioned for R⁴².

The alkanediyl group in L⁴⁴ is preferably an alkanediyl group having 2to 4 carbon atoms, and more preferably an ethylene group.

The structural unit represented by formula (a4-2) includes, for example,structural units represented by formula (a4-1-1) to formula (a4-1-11). Astructural unit in which a methyl group corresponding to R^(f5) in thestructural unit (a4-2) is substituted with a hydrogen atom is alsoexemplified as the structural unit represented by formula (a4-2):

wherein, in formula (a4-3),

R^(f7) represents a hydrogen atom or a methyl group,

L³ represents an alkanediyl group having 1 to 6 carbon atoms,

A^(f13) represents a divalent saturated hydrocarbon group having 1 to 18carbon atoms which may have a fluorine atom,

X^(f12) represents *—O—CO— or *—CO—O— (* represents a bonding site toA^(f13)),

A^(f14) represents a saturated hydrocarbon group having 1 to 17 carbonatoms which may have a fluorine atom, and at least one of A^(f13) andA^(f14) has a fluorine atom, and the upper limit of the total number ofcarbon atoms of L⁵, A^(f13) and A^(f14) is 20.

Examples of the alkanediyl group in L³ include those which are the sameas mentioned in the alkanediyl group of A^(a41).

The divalent saturated hydrocarbon group which may have a fluorine atomin A^(f13) is preferably a divalent chain saturated hydrocarbon groupwhich may have a fluorine atom and a divalent alicyclic saturatedhydrocarbon group which may have a fluorine atom, and more preferably aperfluoroalkanediyl group.

Examples of the divalent chain saturated hydrocarbon group which mayhave a fluorine atom include alkanediyl groups such as a methylenegroup, an ethylene group, a propanediyl group, a butanediyl group and apentanediyl group; and perfluoroalkanediyl groups such as adifluoromethylene group, a perfluoroethylene group, aperfluoropropanediyl group, a perfluorobutanediyl group and aperfluoropentanediyl group.

The divalent alicyclic saturated hydrocarbon group which may have afluorine atom may be either monocyclic or polycyclic. Examples of themonocyclic group include a cyclohexanediyl group and aperfluorocyclohexanediyl group. Examples of the polycyclic group includean adamantanediyl group, a norbornanediyl group, aperfluoroadamantanediyl group and the like.

Examples of the saturated hydrocarbon group and the saturatedhydrocarbon group which may have a fluorine atom for A^(f14) include thesame groups as mentioned for R^(a42). Of these groups, preferable arefluorinated alkyl groups such as a trifluoromethyl group, adifluoromethyl group, a methyl group, a perfluoroethyl group, a2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethylgroup, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, apropyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutylgroup, a butyl group, a perfluoropentyl group, a2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl group,a perfluorohexyl group, a heptyl group, a perfluoroheptyl group, anoctyl group and a perfluorooctyl group; a cyclopropylmethyl group, acyclopropyl group, a cyclobutylmethyl group, a cyclopentyl group, acyclohexyl group, a perfluorocyclohexyl group, an adamantyl group, anadamantylmethyl group, an adamantyldimethyl group, a norbornyl group, anorbornylmethyl group, a perfluoroadamantyl group, aperfluoroadamantylmethyl group and the like.

In formula (a4-3), L⁵ is preferably an ethylene group. The divalentsaturated hydrocarbon group of A^(f13) is preferably a group including adivalent chain saturated hydrocarbon group having 1 to 6 carbon atomsand a divalent alicyclic saturated hydrocarbon group having 3 to 12carbon atoms, and more preferably a divalent chain saturated hydrocarbongroup having 2 to 3 carbon atoms.

The saturated hydrocarbon group of A^(f14) is preferably a groupincluding a chain saturated hydrocarbon group having 3 to 12 carbonatoms and an alicyclic saturated hydrocarbon group having 3 to 12 carbonatoms, and more preferably a group including a chain saturatedhydrocarbon group having 3 to 10 carbon atoms and an alicyclic saturatedhydrocarbon group having 3 to 10 carbon atoms. Of these groups, A^(f14)is preferably a group including an alicyclic saturated hydrocarbon grouphaving 3 to 12 carbon atoms, and more preferably a cyclopropylmethylgroup, a cyclopentyl group, a cyclohexyl group, a norbornyl group and anadamantyl group.

The structural unit represented by formula (a4-3) includes, for example,structural units represented by formula (a4-1′-1) to formula (a4-1′-11).A structural unit in which a methyl group corresponding to R^(f7) in thestructural unit (a4-3) is substituted with a hydrogen atom is alsoexemplified as the structural unit represented by formula (a4-3).

It is also possible to exemplify, as the structural unit (a4), astructural unit represented by formula (a4-4):

wherein, in formula (a4-4),

R^(f21) represents a hydrogen atom or a methyl group,

A^(f21) represents —(CH₂)_(j1)—, —(CH₂)_(j2)—O—(CH₂)_(j3)— or—(CH₂)_(j4)—CO—O— (CH₂)_(j5)—,

j1 to j5 each independently represent an integer of 1 to 6, and

R^(f22) represents a saturated hydrocarbon group having 1 to 10 carbonatoms having a fluorine atom.

Examples of the saturated hydrocarbon group of R^(f22) include thosewhich are the same as the saturated hydrocarbon group represented byR^(a42). R^(f22) is preferably an alkyl group having 1 to 10 carbonatoms having a fluorine atom or an alicyclic saturated hydrocarbon grouphaving 1 to 10 carbon atoms having a fluorine atom, more preferably analkyl group having 1 to 10 carbon atoms having a fluorine atom, andstill more preferably an alkyl group having 1 to 6 carbon atoms having afluorine atom.

In formula (a4-4), A^(f21) is preferably —(CH₂)_(j1)—, more preferablyan ethylene group or a methylene group, and still more preferably amethylene group.

The structural unit represented by formula (a4-4) includes, for example,the following structural units and structural units in which a methylgroup corresponding to R^(f21) in the structural unit (a4-4) issubstituted with a hydrogen atom in structural units represented by thefollowing formulas.

When the resin (A) includes the structural unit (a4), the content ispreferably 1 to 20 mol %, more preferably 2 to 15 mol %, and still morepreferably 3 to 10 mol %, based on all structural units of the resin(A).

<Structural Unit (a5)>

Examples of a non-leaving hydrocarbon group possessed by the structuralunit (a5) include groups having a linear, branched or cyclic hydrocarbongroup. Of these, the structural unit (a5) is preferably a group havingan alicyclic hydrocarbon group.

The structural unit (a5) includes, for example, a structural unitrepresented by formula (a5-1):

wherein, in formula (a5-1),

R⁵¹ represents a hydrogen atom or a methyl group,

R⁵² represents an alicyclic hydrocarbon group having 3 to 18 carbonatoms, and a hydrogen atom included in the alicyclic hydrocarbon groupmay be substituted with an aliphatic hydrocarbon group having 1 to 8carbon atoms, and

L⁵⁵ represents a single bond or a divalent saturated hydrocarbon grouphaving 1 to 18 carbon atoms, and —CH₂— included in the saturatedhydrocarbon group may be replaced by —O— or —CO—.

The alicyclic hydrocarbon group in R⁵² may be either monocyclic orpolycyclic. The monocyclic alicyclic hydrocarbon group includes, forexample, a cyclopropyl group, a cyclobutyl group, a cyclopentyl groupand a cyclohexyl group. The polycyclic alicyclic hydrocarbon groupincludes, for example, an adamantyl group and a norbornyl group.

The aliphatic hydrocarbon group having 1 to 8 carbon atoms includes, forexample, alkyl groups such as a methyl group, an ethyl group, a propylgroup, an isopropyl group, a butyl group, a sec-butyl group, atert-butyl group, a pentyl group, a hexyl group, an octyl group and a2-ethylhexyl group.

Examples of the alicyclic hydrocarbon group having a substituentincludes a 3-methyladamantyl group and the like.

R⁵² is preferably an unsubstituted alicyclic hydrocarbon group having 3to 18 carbon atoms, and more preferably an adamantyl group, a norbornylgroup or a cyclohexyl group.

Examples of the divalent saturated hydrocarbon group in L⁵⁵ include adivalent chain saturated hydrocarbon group and a divalent alicyclicsaturated hydrocarbon group, and a divalent chain saturated hydrocarbongroup is preferable.

The divalent chain saturated hydrocarbon group includes, for example,alkanediyl groups such as a methylene group, an ethylene group, apropanediyl group, a butanediyl group and a pentanediyl group.

The divalent alicyclic saturated hydrocarbon group may be eithermonocyclic or polycyclic. Examples of the monocyclic alicyclic saturatedhydrocarbon group include cycloalkanediyl groups such as acyclopentanediyl group and a cyclohexanediyl group. Examples of thepolycyclic divalent alicyclic saturated hydrocarbon group include anadamantanediyl group and a norbornanediyl group.

The group in which —CH₂— included in the divalent saturated hydrocarbongroup represented by L⁵³ is replaced by —O— or —CO— includes, forexample, groups represented by formula (L1-1) to formula (L1-4). In thefollowing formulas, * and ** each represent a bonding site, and *represents a bonding site to an oxygen atom.

In formula (L1-1),

X^(x1) represents *—O—CO— or *—CO—O— (* represents a bonding site toL^(x1)),

L^(x1) represents a divalent aliphatic saturated hydrocarbon grouphaving 1 to 16 carbon atoms,

L^(x2) represents a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 15 carbon atoms, and the total number ofcarbon atoms of L^(x1) and L^(x2) is 16 or less.

In formula (L1-2),

L^(x3) represents a divalent aliphatic saturated hydrocarbon grouphaving 1 to 17 carbon atoms,

L^(x4) represents a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 16 carbon atoms, and

the total number of carbon atoms of L^(x3) and L^(x4) is 17 or less.

In formula (L1-3),

L^(x5) represents a divalent aliphatic saturated hydrocarbon grouphaving 1 to 15 carbon atoms,

L^(x6) and L^(x7) each independently represent a single bond or adivalent aliphatic saturated hydrocarbon group having 1 to 14 carbonatoms, and

the total number of carbon atoms of L^(x5), L^(x6) and L^(x7) is 15 orless.

In formula (L1-4),

L^(x8) and L^(x9) represents a single bond or a divalent aliphaticsaturated hydrocarbon group having 1 to 12 carbon atoms,

W^(x1) represents a divalent alicyclic saturated hydrocarbon grouphaving 3 to 15 carbon atoms, and the total number of carbon atoms ofL^(x8), L^(x9) and W^(x1) is 15 or less.

L^(x1) is preferably a divalent aliphatic saturated hydrocarbon grouphaving 1 to 8 carbon atoms, and more preferably a methylene group or anethylene group.

L^(x2) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms, and more preferably asingle bond.

L^(x3) is preferably a divalent aliphatic saturated hydrocarbon grouphaving 1 to 8 carbon atoms.

L^(x4) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms.

L^(x5) is preferably a divalent aliphatic saturated hydrocarbon grouphaving 1 to 8 carbon atoms, and more preferably a methylene group or anethylene group.

L^(x6) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms, and more preferably amethylene group or an ethylene group.

L^(x7) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms.

L^(x8) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms, and more preferably asingle bond or a methylene group.

L^(x9) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms, and more preferably asingle bond or a methylene group.

W^(x1) is preferably a divalent alicyclic saturated hydrocarbon grouphaving 3 to 10 carbon atoms, and more preferably a cyclohexanediyl groupor an adamantanediyl group.

The group represented by formula (L1-1) includes, for example, thefollowing divalent groups.

The group represented by formula (L1-2) includes, for example, thefollowing divalent groups.

The group represented by formula (L1-3) includes, for example, thefollowing divalent groups.

The group represented by formula (L1-4) includes, for example, thefollowing divalent groups.

L⁵³ is preferably a single bond or a group represented by formula(L1-1).

Examples of the structural unit (a5-1) include the following structuralunits and structural units in which a methyl group corresponding to R⁵¹in the structural unit (a5-1) in the following structural units issubstituted with a hydrogen atom.

When the resin (A) includes the structural unit (a5), the content ispreferably 1 to 30 mol %, more preferably 2 to 20 mol %, and still morepreferably 3 to 15 mol %, based on all structural units of the resin(A).

<Structural Unit (II)>

The resin (A) may further include a structural unit which is decomposedupon exposure to radiation to generate an acid (hereinafter sometimesreferred to as “structural unit (II)”). Specific examples of thestructural unit (II) include the structural units mentioned in JP2016-79235 A, and a structural unit having a sulfonate group or acarboxylate group and an organic cation in a side chain or a structuralunit having a sulfonio group and an organic anion in a side chain arepreferable.

The structural unit having a sulfonate group or a carboxylate group andan organic cation in a side chain is preferably a structural unitrepresented by formula (II-2-A′):

wherein, in formula (II-2-A′),

X^(III3) represents a divalent saturated hydrocarbon group having 1 to18 carbon atoms, —CH₂— included in the saturated hydrocarbon group maybe replaced by —O—, —S— or —CO—, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a halogen atom, analkyl group having 1 to 6 carbon atoms which may have a halogen atom, ora hydroxy group,

A^(x1) represents an alkanediyl group having 1 to 8 carbon atoms, and ahydrogen atom included in the alkanediyl group may be substituted with afluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms,

RA⁻ represents a sulfonate group or a carboxylate group,

R^(III3) represents a hydrogen atom, a halogen atom or an alkyl grouphaving 1 to 6 carbon atoms which may have a halogen atom, and

ZA⁺ represents an organic cation.

Examples of the halogen atom represented by R^(III3) include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom.

Examples of the alkyl group having 1 to 6 carbon atoms which may have ahalogen atom represented by R^(III3) include those which are the same asthe alkyl group having 1 to 6 carbon atoms which may have a halogen atomrepresented by R^(a8).

Examples of the alkanediyl group having 1 to 8 carbon atoms representedby A^(x1) include a methylene group, an ethylene group, apropane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group, an ethane-1,1-diyl group, apropane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diylgroup, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, a2-methylbutane-1,4-diyl group and the like.

Examples of the perfluoroalkyl group having 1 to 6 carbon atoms whichmay be substituted in A^(x1) include a trifluoromethyl group, aperfluoroethyl group, a perfluoropropyl group, a perfluoroisopropylgroup, a perfluorobutyl group, a perfluorosec-butyl group, aperfluorotert-butyl group, a perfluoropentyl group, a perfluorohexylgroup and the like.

Examples of the divalent saturated hydrocarbon group having 1 to 18carbon atoms represented by X^(III3) include a linear or branchedalkanediyl group, a monocyclic or a polycyclic divalent alicyclicsaturated hydrocarbon group, or a combination thereof.

Specific examples thereof include linear alkanediyl groups such as amethylene group, an ethylene group, a propane-1,3-diyl group, apropane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group, a heptane-1,7-diyl group, anoctane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diylgroup, an undecane-1,11-diyl group and a dodecane-1,12-diyl group;branched alkanediyl groups such as a butane-1,3-diyl group, a2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, apentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group;

divalent monocyclic alicyclic saturated hydrocarbon groups, for example,cycloalkanediyl groups such as a cyclobutane-1,3-diyl group, acyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group and acyclooctane-1,5-diyl group; and divalent polycyclic alicyclic saturatedhydrocarbon groups such as a norbornane-1,4-diyl group, anorbornane-2,5-diyl group, an adamantane-1,5-diyl group and anadamantane-2,6-diyl group.

Those in which —CH₂— included in the saturated hydrocarbon group arereplaced by —O—, —S— or —CO— include, for example, divalent groupsrepresented by formula (X1) to formula (X53). Before replacing —CH₂—included in the saturated hydrocarbon group by —O—, —S— or —CO—, thenumber of carbon atoms is 17 or less. In the following formulas, * and** represent a bonding site, and * represents a bonding site to A^(x1).

X³ represents a divalent saturated hydrocarbon group having 1 to 16carbon atoms.

X⁴ represents a divalent saturated hydrocarbon group having 1 to 15carbon atoms.

X⁵ represents a divalent saturated hydrocarbon group having 1 to 13carbon atoms.

X⁶ represents a divalent saturated hydrocarbon group having 1 to 14carbon atoms.

X⁷ represents a trivalent saturated hydrocarbon group having 1 to 14carbon atoms.

X⁸ represents a divalent saturated hydrocarbon group having 1 to 13carbon atoms.

Examples of the organic cation represented by ZA⁺ include an organiconium cation, an organic sulfonium cation, an organic iodonium cation,an organic ammonium cation, a benzothiazolium cation and an organicphosphonium cation. Of these organic cations, an organic sulfoniumcation and an organic iodonium cation are preferable, and anarylsulfonium cation is more preferable. Specific examples thereofinclude a cation represented by any one of the above-mentioned formula(b2-1) to formula (b2-4) (hereinafter sometimes referred to as “cation(b2-1)” according to the number of formula.)

The structural unit represented by formula (II-2-A′) is preferably astructural unit represented by formula (II-2-A):

wherein, in formula (II-2-A), R^(III3), X^(III3) and ZA⁺ are the same asdefined above,

z represents an integer of 0 to 6,

R^(III2) and R^(III4) each independently represent a hydrogen atom, afluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms, andwhen z is 2 or more, a plurality of R^(III2) and R^(III4) may be thesame or different form each other, and

Q^(a) and Q^(b) each independently represent a fluorine atom or aperfluoroalkyl group having 1 to 6 carbon atoms.

Examples of the perfluoroalkyl group having 1 to 6 carbon atomsrepresented by R^(III2), R^(III4), Q^(a) and Q^(b) include those whichare the same as the below-mentioned perfluoroalkyl group having 1 to 6carbon atoms represented by Q^(b1).

The structural unit represented by formula (II-2-A) is preferably astructural unit represented by formula (II-2-A-1):

wherein, in formula (II-2-A-1),

R^(III2), R^(III3), R^(III4), Q^(a), Q^(b), z and ZA⁺ are the same asdefined above,

R^(III5) represents a saturated hydrocarbon group having 1 to 12 carbonatoms, and

X¹² represents a divalent saturated hydrocarbon group having 1 to 11carbon atoms, —CH₂— included in the saturated hydrocarbon group may bereplaced by —O—, —S— or —CO—, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a halogen atom or ahydroxy group.

Examples of the saturated hydrocarbon group having 1 to 12 carbon atomsrepresented by R^(III5) include linear or branched alkyl groups such asa methyl group, an ethyl group, a propyl group, an isopropyl group, abutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a nonyl group, a decylgroup, an undecyl group and a dodecyl group.

Examples of the divalent saturated hydrocarbon group represented byX^(I2) include those which are the same as the divalent saturatedhydrocarbon group represented by X^(III3).

The structural unit represented by formula (II-2-A-1) is preferably astructural unit represented by formula (II-2-A-2):

wherein, in formula (II-2-A-2), R^(III3), R^(III5) and ZA⁺ are the sameas defined above, and

m and nA each independently represent 1 or 2.

The structural unit represented by formula (II-2-A′) includes, forexample, the following structural units, structural units in which agroup corresponding to a methyl group of R^(III3) is substituted with analkyl group having 1 to 6 carbon atoms which may have a hydrogen atom, ahalogen atom (e.g., fluorine atom) or a halogen atom (e.g.,trifluoromethyl group, etc.) and the structural units mentioned in WO2012/050015 A. ZA⁺ represents an organic cation.

The structural unit having a sulfonio group and an organic anion in aside chain is preferably a structural unit represented by formula(II-1-1):

wherein, in formula (II-1-1),

A^(II1) represents a single bond or a divalent linking group,

R^(II1) represents a divalent aromatic hydrocarbon group having 6 to 18carbon atoms,

R^(II2) and R^(II3) each independently represent a hydrocarbon grouphaving 1 to 18 carbon atoms, and R^(II2) and R^(II3) may be bonded toeach other to form a ring together with sulfur atoms to which R^(II2)and R^(II3) are bonded,

R^(II4) represents a hydrogen atom, a halogen atom or an alkyl grouphaving 1 to 6 carbon atoms which may have a halogen atom, and

A⁻ represents an organic anion.

Examples of the divalent aromatic hydrocarbon group having 6 to 18carbon atoms represented by R^(II1) include a phenylene group and anaphthylene group.

Examples of the hydrocarbon group represented by R^(II2) and R^(II3)include an alkyl group, an alicyclic hydrocarbon group, an aromatichydrocarbon group, and groups obtained by combining these groups.

Examples of the alkyl group and the alicyclic hydrocarbon group includethose which are the same as mentioned above.

Examples of the aromatic hydrocarbon group include aryl groups such as aphenyl group, a naphthyl group, an anthryl group, a biphenyl group and aphenanthryl group.

Examples of the combined group include groups obtained by combining theabove-mentioned alkyl group and alicyclic hydrocarbon group, aralkylgroups such as a benzyl group, aromatic hydrocarbon groups having analkyl group (a p-methylphenyl group, a p-tert-butylphenyl group, a tolylgroup, a xylyl group, a cumenyl group, a mesityl group, a2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group, etc.), aromatichydrocarbon groups having an alicyclic hydrocarbon group (ap-cyclohexylphenyl group, a p-adamantylphenyl group, etc.),aryl-cycloalkyl groups such as a phenylcyclohexyl group, and the like.

Examples of the halogen atom represented by R^(II4) include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom.

Examples of the alkyl group having 1 to 6 carbon atoms which may have ahalogen atom represented by R^(II4) include those which are the same asthe alkyl group having 1 to 6 carbon atoms which may have a halogen atomrepresented by R^(a8).

Examples of the divalent linking group represented by A^(II1) include adivalent saturated hydrocarbon group having 1 to 18 carbon atoms, and—CH₂— included in the divalent saturated hydrocarbon group may bereplaced by —O—, —S— or —CO—. Specific examples thereof include thosewhich are the same as the divalent saturated hydrocarbon group having 1to 18 carbon atoms represented by X^(III3).

Examples of the structural unit including a cation in formula (II-1-1)include the following structural units, structural units in which agroup corresponding to a methyl group of R^(II4) is substituted with ahydrogen atom, a halogen atom (e.g., fluorine atom) or an alkyl grouphaving 1 to 6 carbon atoms which may have a halogen atom (e.g.,trifluoromethyl group, etc.).

Examples of the organic anion represented by A⁻ include a sulfonic acidanion, a sulfonylimide anion, a sulfonylmethide anion and a carboxylicacid anion. The organic anion represented by A⁻ is preferably a sulfonicacid, and examples of the sulfonic acid anion include those which arethe same as an anion represented by formula (B1) mentioned above.

Examples of the sulfonylimide anion represented by A⁻ include thefollowings.

Examples of the sulfonylmethide anion include the following.

Examples of the carboxylic acid anion include the following.

Examples of the structural unit represented by formula (II-1-1) includestructural units represented by the following formulas.

When the structural unit (II) is included in the resin (A), the contentof the structural unit (II) is preferably 1 to 20 mol %, more preferably2 to 15 mol %, and still more preferably 3 to 10 mol %, based on allstructural units of the resin (A).

The resin (A) may include structural units other than the structuralunits mentioned above, and examples of such structural unit includestructural units well-known in the art.

The resin (A) is preferably a resin composed of a structural unit (a1)and a structural unit (s), i.e., a copolymer of a monomer (a1) and amonomer (s).

The structural unit (a1) is preferably at least one selected from thegroup consisting of a structural unit (a1-0), a structural unit (a1-1)and a structural unit (a1-2) (preferably the structural unit having acyclohexyl group, and a cyclopentyl group), more preferably at leasttwo, and still more preferably at least two selected from the groupconsisting of a structural unit (a1-1) and a structural unit (a1-2).

The structural unit (s) is preferably at least one selected from thegroup consisting of a structural unit (a2) and a structural unit (a3).The structural unit (a2) is preferably a structural unit represented byformula (a2-1) or a structural unit represented by formula (a2-A). Thestructural unit (a3) is preferably at least one selected from the groupconsisting of a structural unit represented by formula (a3-1), astructural unit represented by formula (a3-2) and a structural unitrepresented by formula (a3-4).

The respective structural units constituting the resin (A) may be usedalone, or two or more structural units may be used in combination. Usinga monomer from which these structural units are derived, it is possibleto produce by a known polymerization method (e.g. radical polymerizationmethod). The content of the respective structural units included in theresin (A) can be adjusted according to the amount of the monomer used inthe polymerization.

The weight-average molecular weight of the resin (A) is preferably 2,000or more (more preferably 2,500 or more, and still more preferably 3,000or more), and 50,000 or less (more preferably 30,000 or less, and stillmore preferably 15,000 or less). In the present specification, theweight-average molecular weight is a value determined by gel permeationchromatography under the conditions mentioned in Examples.

<Resin Other than Resin (A)>

The resist composition according to some embodiments of the presentdisclosure may include the resin other than the resin (A).

The resin other than the resin (A) includes, for example, a resinincluding a structural unit (a4) or a structural unit (a5) (hereinaftersometimes referred to as resin (X)).

The resin (X) is preferably a resin including a structural unit (a4),particularly.

In the resin (X), the content of the structural unit (a4) is preferably30 mol % or more, more preferably 40 mol % or more, and still morepreferably 45 mol % or more, based on the total of all structural unitsof the resin (X).

Examples of the structural unit, which may be further included in theresin (X), include a structural unit (a2), a structural unit (a3) andstructural units derived from other known monomers. Particularly, theresin (X) is preferably a resin composed only of a structural unit (a4)and/or a structural unit (a5), and more preferably a resin composed onlyof a structural unit (a4).

The respective structural unit constituting the resin (X) may be usedalone, or two or more structural units may be used in combination. Usinga monomer from which these structural units are derived, it is possibleto produce by a known polymerization method (e.g. radical polymerizationmethod). The content of the respective structural units included in theresin (X) can be adjusted according to the amount of the monomer used inthe polymerization.

The weight-average molecular weight of the resin (X) is preferably 6,000or more (more preferably 7,000 or more) and 80,000 or less (morepreferably 60,000 or less). The measurement means of the weight-averagemolecular weight of the resin (X) is the same as in the case of theresin (A).

When the resist composition includes the resin (X), the content ispreferably 1 to 60 parts by mass, more preferably 1 to 50 parts by mass,still more preferably 1 to 40 parts by mass, yet more preferably 1 to 30parts by mass, and further preferably 1 to 8 parts by mass, based on 100parts by mass of the resin (A).

The content of the resin (A) in the resist composition is preferably 80%by mass or more and 99% by mass or less, and more preferably 90% by massor more and 99% by mass or less, based on the solid component of theresist composition. When including resins other than the resin (A), thetotal content of the resin (A) and resins other than the resin (A) ispreferably 80% by mass or more and 99% by mass or less, and morepreferably 90% by mass or more and 99% by mass or less, based on thesolid component of the resist composition. The solid component of theresist composition and the content of the resin thereto can be measuredby a known analysis means such as liquid chromatography or gaschromatography.

<Acid Generator (B)>

Either nonionic or ionic acid generator may be used as the acidgenerator (B). Examples of the nonionic acid generator include sulfonateesters (e.g., 2-nitrobenzyl ester, aromatic sulfonate, oxime sulfonate,N-sulfonyloxyimide, sulfonyloxyketone, diazonaphthoquinone 4-sulfonate),sulfones (e.g., disulfone, ketosulfone, sulfonyldiazomethane) and thelike. Typical examples of the ionic acid generator include onium saltscontaining an onium cation (e.g., diazonium salt, phosphonium salt,sulfonium salt, iodonium salt). Examples of the anion of the onium saltinclude sulfonic acid anion, sulfonylimide anion, sulfonylmethide anionand the like.

Specific examples of the acid generator (B) include compounds generatingan acid upon exposure to radiation mentioned in JP 63-26653 A, JP55-164824 A, JP 62-69263 A, JP 63-146038 A, JP 63-163452 A, JP 62-153853A, JP 63-146029 A, U.S. Pat. Nos. 3,779,778, 3,849,137, DE Patent No.3914407 and EP Patent No. 126,712. Compounds produced by a known methodmay also be used. Two or more acid generators (B) may also be used incombination.

The acid generator (B) is preferably a fluorine-containing acidgenerator, and more preferably a salt represented by formula (B1)(hereinafter sometimes referred to as “acid generator (B1)”):

wherein, in formula (B1),

Q^(b1) and Q^(b2) each independently represent a fluorine atom or aperfluoroalkyl group having 1 to 6 carbon atoms,

L^(b1) represents a divalent saturated hydrocarbon group having 1 to 24carbon atoms, —CH₂— included in the divalent saturated hydrocarbon groupmay be replaced by —O— or —CO—, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group,

Y represents a methyl group which may have a substituent or an alicyclichydrocarbon group having 3 to 24 carbon atoms which may have asubstituent, and —CH₂— included in the alicyclic hydrocarbon group maybe replaced by —O—, —S(O)₂— or —CO—, and Z1⁺ represents an organiccation.

Examples of the perfluoroalkyl group represented by Q^(b1) and Q^(b2)include a trifluoromethyl group, a perfluoroethyl group, aperfluoropropyl group, a perfluoroisopropyl group, a perfluorobutylgroup, a perfluorosec-butyl group, a perfluorotert-butyl group, aperfluoropentyl group and a perfluorohexyl group.

Preferably, Q^(b1) and Q^(b2) are each independently a fluorine atom ora trifluoromethyl group, and more preferably, both are fluorine atoms.

Examples of the divalent saturated hydrocarbon group in L^(b1) include alinear alkanediyl group, a branched alkanediyl group, and a monocyclicor polycyclic divalent alicyclic saturated hydrocarbon group, or thedivalent saturated hydrocarbon group may be a group formed by combiningtwo or more of these groups.

Specific examples thereof include linear alkanediyl groups such as amethylene group, an ethylene group, a propane-1,3-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diylgroup, a heptane-1,7-diyl group, an octane-1,8-diyl group, anonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diylgroup, a dodecane-1,12-diyl group, a tridecane-1,13-diyl group, atetradecane-1,14-diyl group, a pentadecane-1,15-diyl group, ahexadecane-1,16-diyl group and a heptadecane-1,17-diyl group;

branched alkanediyl groups such as an ethane-1,1-diyl group, apropane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diylgroup, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a2-methylbutane-1,4-diyl group;

monocyclic divalent alicyclic saturated hydrocarbon groups which arecycloalkanediyl groups such as a cyclobutane-1,3-diyl group, acyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group and acyclooctane-1,5-diyl group; and

polycyclic divalent alicyclic saturated hydrocarbon groups such as anorbornane-1,4-diyl group, a norbornane-2,5-diyl group, anadamantane-1,5-diyl group and an adamantane-2,6-diyl group.

The group in which —CH₂— included in the divalent saturated hydrocarbongroup represented by L^(b1) is replaced by —O— or —CO— includes, forexample, a group represented by any one of formula (b1-1) to formula(b1-3). In groups represented by formula (b1-1) to formula (b1-3) andgroups represented by formula (b1-4) to formula (b1-11) which arespecific examples thereof, * and ** represent a bond, and * represents abond to —Y.

In formula (b1-1),

L^(b2) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 22 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom,

L^(b3) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 22 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group, and —CH₂— included in the saturated hydrocarbon group maybe replaced by —O— or —CO—, and

the total number of carbon atoms of L^(b2) and L^(b3) is 22 or less.

In formula (b1-2),

L^(b4) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 22 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom,

L^(b5) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 22 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group, and —CH₂— included in the saturated hydrocarbon group maybe replaced by —O— or —CO—, and

the total number of carbon atoms of L^(b4) and L^(b5) is 22 or less.

In formula (b1-3),

L^(b6) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 23 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group,

L^(b7) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 23 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group, and —CH₂— included in the saturated hydrocarbon group maybe replaced by —O— or —CO—,

the total number of carbon atoms of L^(b6) and L^(b7) is 23 or less, and

* and ** represent a bond, and * represents a bond to Y.

In groups represented by formula (b1-1) to formula (b1-3), when —CH₂—included in the saturated hydrocarbon group is replaced by —O— or —CO—,the number of carbon atoms before replacement is taken as the number ofcarbon atoms of the saturated hydrocarbon group.

Examples of the divalent saturated hydrocarbon group include those whichare the same as the divalent saturated hydrocarbon group of L^(b1).

L^(b2) is preferably a single bond.

L^(b3) is preferably a divalent saturated hydrocarbon group having 1 to4 carbon atoms.

L^(b4) is preferably a divalent saturated hydrocarbon group having 1 to8 carbon atoms, and a hydrogen atom included in the divalent saturatedhydrocarbon group may be substituted with a fluorine atom.

L^(b3) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 8 carbon atoms.

L^(b6) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 4 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom.

L^(b7) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 18 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group, and —CH₂— included in the divalent saturated hydrocarbongroup may be replaced by —O— or —CO—.

The group in which —CH₂— included in the divalent saturated hydrocarbongroup represented by L^(b1) is replaced by —O— or —CO— is preferably agroup represented by formula (b1-1) or formula (b1-3).

Examples of the group represented by formula (b1-1) include groupsrepresented by formula (b1-4) to formula (b1-8).

In formula (b1-4),

L^(b8) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 22 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group.

In formula (b1-5),

L^(b9) represents a divalent saturated hydrocarbon group having 1 to 20carbon atoms, and —CH₂— included in the divalent saturated hydrocarbongroup may be replaced by —O— or —CO—.

L^(b10) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 19 carbon atoms, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group, and

the total number of carbon atoms of L^(b9) and L^(b10) is 20 or less.

In formula (b1-6),

L^(b11) represents a divalent saturated hydrocarbon group having 1 to 21carbon atoms,

L^(b12) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 20 carbon atoms, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group, and the total number of carbon atoms of L^(b11)and L^(b12) is 21 or less.

In formula (b1-7),

L^(b13) represents a divalent saturated hydrocarbon group having 1 to 19carbon atoms,

L^(b14) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 18 carbon atoms, and —CH₂— included in the divalentsaturated hydrocarbon group may be replaced by —O— or —CO—,

L^(b12) is represents a single bond or a divalent saturated hydrocarbongroup having 1 to 18 carbon atoms, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group, and

the total number of carbon atoms of L^(b13) to L^(b15) is 19 or less.

In formula (b1-8),

L^(b16) represents a divalent saturated hydrocarbon group having 1 to 18carbon atoms, and —CH₂— included in the divalent saturated hydrocarbongroup may be replaced by —O— or —CO—,

L^(b17) represents a divalent saturated hydrocarbon group having 1 to 18carbon atoms,

L^(b18) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 17 carbon atoms, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group, and the total number of carbon atoms of L^(b16)to L^(b18) is 19 or less.

* and ** represent a bond, and * represents a bond to Y.

L^(b8) is preferably a divalent saturated hydrocarbon group having 1 to4 carbon atoms.

L^(b9) is preferably a divalent saturated hydrocarbon group having 1 to8 carbon atoms.

L^(b10) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 19 carbon atoms, and more preferably a single bond ora divalent saturated hydrocarbon group having 1 to 8 carbon atoms.

L^(b11) is preferably a divalent saturated hydrocarbon group having 1 to8 carbon atoms.

L^(b12) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 8 carbon atoms.

L^(b13) is preferably a divalent saturated hydrocarbon group having 1 to12 carbon atoms.

L^(b14) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 6 carbon atoms.

L^(b15) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 18 carbon atoms, and more preferably a single bond ora divalent saturated hydrocarbon group having 1 to 8 carbon atoms.

L^(b16) is preferably a divalent saturated hydrocarbon group having 1 to12 carbon atoms.

L^(b17) is preferably a divalent saturated hydrocarbon group having 1 to6 carbon atoms.

L^(b18) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 17 carbon atoms, and more preferably a single bond ora divalent saturated hydrocarbon group having 1 to 4 carbon atoms.

Examples of the group represented by formula (b1-3) include groupsrepresented by formula (b1-9) to formula (b1-11).

In formula (b1-9),

L^(b19) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 23 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom,

L^(b20) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 23 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom, ahydroxy group or an alkylcarbonyloxy group, —CH₂— included in thealkylcarbonyloxy group may be replaced by —O— or —CO—, and a hydrogenatom included in the alkylcarbonyloxy group may be substituted with ahydroxy group, and

the total number of carbon atoms of L^(b19) and L^(b20) is 23 or less.

In formula (b1-10),

L^(b21) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 21 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom,

L^(b22) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 21 carbon atoms,

L^(b23) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 21 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom, ahydroxy group or an alkylcarbonyloxy group, —CH₂— included in thealkylcarbonyloxy group may be replaced by —O— or —CO—, and a hydrogenatom included in the alkylcarbonyloxy group may be substituted with ahydroxy group, and

the total number of carbon atoms of L^(b21), L^(b22) and L^(b23) is 21or less.

* and ** represent a bond, and * represents a bond to Y.

In formula (b1-11),

L^(b24) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 20 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom,

L^(b25) represents a divalent saturated hydrocarbon group having 1 to 21carbon atoms,

L^(b26) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 20 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom, ahydroxy group or an alkylcarbonyloxy group, —CH₂— included in thealkylcarbonyloxy group may be replaced by —O— or —CO—, and a hydrogenatom included in the alkylcarbonyloxy group may be substituted with ahydroxy group, the total number of carbon atoms of L^(b24), L^(b25) andL^(b26) is 21 or less.

In groups represented by formula (b1-9) to formula (b1-11), when ahydrogen atom included in the saturated hydrocarbon group is substitutedwith an alkylcarbonyloxy group, the number of carbon atoms beforesubstitution is taken as the number of carbon atoms of the saturatedhydrocarbon group.

Examples of the alkylcarbonyloxy group include an acetyloxy group, apropionyloxy group, a butyryloxy group, a cyclohexylcarbonyloxy group,an adamantylcarbonyloxy group and the like.

Examples of the group represented by formula (b1-4) include thefollowings:

* and ** represent a bond, and * represents a bond to Y.

Examples of the group represented by formula (b1-5) include thefollowings:

* and ** represent a bond, and * represents a bond to Y.

Examples of the group represented by formula (b1-6) include thefollowings:

* and ** represent a bond, and * represents a bond to Y.

Examples of the group represented by formula (b1-7) include thefollowings:

* and ** represent a bond, and * represents a bond to Y.

Examples of the group represented by formula (b1-8) include thefollowings

* and ** represent a bond, and * represents a bond to Y.

Examples of the group represented by formula (b1-2) include thefollowings:

* and ** represent a bond, and * represents a bond to Y.

Examples of the group represented by formula (b1-9) include thefollowings:

* and ** represent a bond, and * represents a bond to Y.

Examples of the group represented by formula (b1-10) include thefollowings:

* and ** represent a bond, and * represents a bond to Y.

Examples of the group represented by formula (b1-11) include thefollowings:

* and ** represent a bond, and * represents a bond to Y.

Examples of the alicyclic hydrocarbon group represented by Y includegroups represented by formula (Y1) to formula (Y11) and formula (Y36) toformula (Y38).

When —CH₂— included in the alicyclic hydrocarbon group represented by Yis replaced by —O—, —S(O)₂— or —CO—, the number may be 1, or 2 or more.Examples of such group include groups represented by formula (Y12) toformula (Y35) and formula (Y39) to formula (Y43).

The alicyclic hydrocarbon group represented by Y is preferably a grouprepresented by any one of formula (Y1) to formula (Y20), formula (Y26),formula (Y27), formula (Y30), formula (Y31) and formula (Y39) to formula(Y43), more preferably a group represented by formula (Y11), formula(Y15), formula (Y16), formula (Y20), formula (Y26), formula (Y27),formula (Y30), formula (Y31), formula (Y39), formula (Y40), formula(Y42) or formula (Y43), and still more preferably a group represented byformula (Y11), formula (Y15), formula (Y20), formula (Y26), formula(Y27), formula (Y30), formula (Y31), formula (Y39), formula (Y40),formula (Y42) or formula (Y43).

When the alicyclic hydrocarbon group represented by Y is a spiro ringcontaining an oxygen atom, such as formula (Y28) to formula (Y35),formula (Y39) to formula (Y40), formula (Y42) or formula (Y43), thealkanediyl group between two oxygen atoms preferably has one or morefluorine atoms. Of alkanediyl groups included in a ketal structure, itis preferable that a methylene group adjacent to the oxygen atom is notsubstituted with a fluorine atom.

Examples of the substituent of the methyl group represented by Y includea halogen atom, a hydroxy group, an alicyclic hydrocarbon group having 3to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbonatoms, a glycidyloxy group, a —(CH₂)_(ja)—CO—O—R^(b1) group or a—(CH₂)_(ja)—O—CO—R^(b1) group (wherein R^(b1) represents an alkyl grouphaving 1 to 16 carbon atoms, an alicyclic hydrocarbon group having 3 to16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbonatoms, or a group obtained by combining these groups, —CH₂— included inthe alkyl group and the alicyclic hydrocarbon group may be replaced by—O—, —SO₂— or —CO—, a hydrogen atom included in the alkyl group, thealicyclic hydrocarbon group and the aromatic hydrocarbon group may besubstituted with a hydroxy group or a fluorine atom, and ja representsan integer of 0 to 4).

Examples of the substituent of the alicyclic hydrocarbon grouprepresented by Y include a halogen atom, a hydroxy group, an alkyl grouphaving 1 to 16 carbon atoms which may be substituted with a hydroxygroup (—CH₂— included in the alkyl group may be replaced by —O— or—CO—), an alicyclic hydrocarbon group having 3 to 16 carbon atoms, anaromatic hydrocarbon group having 6 to 18 carbon atoms, an aralkyl grouphaving 7 to 21 carbon atoms, a glycidyloxy group, a—(CH₂)_(ja)—CO—O—R^(b1) group or a —(CH₂)_(ja)—O—CO—R^(b1) group(wherein R^(b1) represents an alkyl group having 1 to 16 carbon atoms,an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatichydrocarbon group having 6 to 18 carbon atoms, or a group obtained bycombining these groups, —CH₂— included in the alkyl group and thealicyclic hydrocarbon group may be replaced by —O—, —SO₂— or —CO—, ahydrogen atom included in the alkyl group, the alicyclic hydrocarbongroup and the aromatic hydrocarbon group may be substituted with ahydroxy group or a fluorine atom, and ja represents an integer of 0 to4).

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of the alicyclic hydrocarbon group include a cyclopentyl group,a cyclohexyl group, a methylcyclohexyl group, a dimethylcyclohexylgroup, a cycloheptyl group, a cyclooctyl group, a norbornyl group, anadamantyl group and the like. The alicyclic hydrocarbon group may have achain hydrocarbon group, and examples thereof include a methylcyclohexylgroup, a dimethylcyclohexyl group and the like. The number of carbonatoms of the alicyclic hydrocarbon group is preferably 3 to 12, and morepreferably 3 to 10.

Examples of the aromatic hydrocarbon group include aryl groups such as aphenyl group, a naphthyl group, an anthryl group, a biphenyl group and aphenanthryl group. The aromatic hydrocarbon group may have a chainhydrocarbon group or an alicyclic hydrocarbon group, and examplesthereof include an aromatic hydrocarbon group which has a chainhydrocarbon group having 1 to 18 carbon atoms (a tolyl group, a xylylgroup, a cumenyl group, a mesityl group, a p-methylphenyl group, ap-ethylphenyl group, a p-tert-butylphenyl group, a 2,6-diethylphenylgroup, a 2-methyl-6-ethylphenyl group, etc.), and an aromatichydrocarbon group which has an alicyclic hydrocarbon group having 3 to18 carbon atoms (a p-adamantylphenyl group, a p-cyclohexylphenyl group,etc.). The number of carbon atoms of the aromatic hydrocarbon group ispreferably 6 to 14, and more preferably 6 to 10.

Examples of the alkyl group include a methyl group, an ethyl group, apropyl group, an isopropyl group, a butyl group, a sec-butyl group, atert-butyl group, a pentyl group, a hexyl group, a heptyl group, a2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, anundecyl group, a dodecyl group and the like. The number of carbon atomsof the alkyl group is preferably 1 to 12, more preferably 1 to 6, andstill more preferably 1 to 4.

Examples of the alkyl group substituted with a hydroxy group includehydroxyalkyl groups such as a hydroxymethyl group and a hydroxyethylgroup.

Examples of the aralkyl group include a benzyl group, a phenethyl group,a phenylpropyl group, a naphthylmethyl group and a naphthylethyl group.

Examples of the group in which —CH₂— included in the alkyl group isreplaced by —O—, —S(O)₂— or —CO— include an alkoxy group, analkoxycarbonyl group, an alkylcarbonyl group, an alkylcarbonyloxy group,or a group obtained by combining these groups.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, aheptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxygroup. The number of carbon atoms of the alkoxy group is preferably 1 to12, more preferably 1 to 6, and still more preferably 1 to 4.

Examples of the alkoxycarbonyl group include a methoxycarbonyl group, anethoxycarbonyl group, a butoxycarbonyl group and the like. The number ofcarbon atoms of the alkoxycarbonyl group is preferably 2 to 12, morepreferably 2 to 6, and still more preferably 2 to 4.

Examples of the alkylcarbonyl group include an acetyl group, a propionylgroup and a butyryl group. The number of carbon atoms of thealkylcarbonyl group is preferably 2 to 12, more preferably 2 to 6, andstill more preferably 2 to 4.

Examples of the alkylcarbonyloxy group include an acetyloxy group, apropionyloxy group, a butyryloxy group and the like. The number ofcarbon atoms of the alkylcarbonyloxy group is preferably 2 to 12, morepreferably 2 to 6, and still more preferably 2 to 4.

Examples of the combined group include a group obtained by combining analkoxy group with an alkyl group, a group obtained by combining analkoxy group with an alkoxy group, a group obtained by combining analkoxy group with an alkylcarbonyl group, a group obtained by combiningan alkoxy group with an alkylcarbonyloxy group and the like.

Examples of the group obtained by combining an alkoxy group with analkyl group include alkoxyalkyl groups such as a methoxymethyl group, amethoxyethyl group, an ethoxyethyl group and an ethoxymethyl group. Thenumber of carbon atoms of the alkoxyalkyl group is preferably 2 to 12,more preferably 2 to 6, and still more preferably 2 to 4.

Examples of the group obtained by combining an alkoxy group with analkoxy group include alkoxyalkoxy groups such as a methoxymethoxy group,a methoxyethoxy group, an ethoxymethoxy group and an ethoxyethoxy group.The number of carbon atoms of the alkoxyalkoxy group is preferably 2 to12, more preferably 2 to 6, and still more preferably 2 to 4.

Examples of the group obtained by combining an alkoxy group with analkylcarbonyl group include alkoxyalkylcarbonyl groups such as amethoxyacetyl group, a methoxypropionyl group, an ethoxyacetyl group andan ethoxypropionyl group. The number of carbon atoms of thealkoxyalkylcarbonyl group is preferably 3 to 13, more preferably 3 to 7,and still more preferably 3 to 5.

Examples of the group obtained by combining an alkoxy group with analkylcarbonyloxy group include alkoxyalkylcarbonyloxy groups such as amethoxyacetyloxy group, a methoxypropionyloxy group, an ethoxyacetyloxygroup and an ethoxypropionyloxy group. The number of carbon atoms of thealkoxyalkylcarbonyloxy group is preferably 3 to 13, more preferably 3 to7, and still more preferably 3 to 5.

Examples of the group in which —CH₂— included in the alicyclichydrocarbon group is replaced by —O—, —S(O)₂— or —CO— include groupsrepresented by formula (Y12) to formula (Y35) and formula (Y39) toformula (Y43).

Examples of Y include the followings.

Y is preferably an alicyclic hydrocarbon group having 3 to 24 carbonatoms which may have a substituent, more preferably an alicyclichydrocarbon group having 3 to 20 carbon atoms which may have asubstituent, still more preferably an alicyclic hydrocarbon group having3 to 18 carbon atoms which may have a substituent, and yet morepreferably an adamantyl group which may have a substituent, and —CH₂—constituting the alicyclic hydrocarbon group or the adamantyl group maybe replaced by —CO—, —S(O)₂— or —CO—. Specifically, Y is preferably anadamantyl group, a hydroxyadamantyl group, an oxoadamantyl group, orgroups represented by formula (Y42), formula (Y100) to formula (Y114).

The anion in the salt represented by formula (B1) is preferably anionsrepresented by formula (B1-A-1) to formula (B1-A-59) [hereinaftersometimes referred to as “anion (B1-A-1)” according to the number offormula], and more preferably an anion represented by any one of formula(B1-A-1) to formula (B1-A-4), formula (B1-A-9), formula (B1-A-10),formula (B1-A-24) to formula (B1-A-33), formula (B1-A-36) to formula(B1-A-40) and formula (B1-A-47) to formula (B1-A-59).

R^(i2) to R^(i7) each independently represent, for example, an alkylgroup having 1 to 4 carbon atoms, and preferably a methyl group or anethyl group. R^(i8) is, for example, a chain hydrocarbon group having 1to 12 carbon atoms, preferably an alkyl group having 1 to 4 carbonatoms, an alicyclic hydrocarbon group having 5 to 12 carbon atoms, or agroup formed by combining these groups, and more preferably a methylgroup, an ethyl group, a cyclohexyl group or an adamantyl group. L^(A41)is a single bond or an alkanediyl group having 1 to 4 carbon atoms.Q^(b1) and Q^(b2) are the same as defined above.

Specific examples of the anion in the salt represented by formula (B1)include anions mentioned in JP 2010-204646 A.

The anion in the salt represented by formula (B1) preferably includesanions represented by formula (B1a-1) to formula (B1a-38).

Of these, an anion represented by any one of formula (B1a-1) to formula(B1a-3) and formula (B1a-7) to formula (B1a-16), formula (B1a-18),formula (B1a-19) and formula (B1a-22) to formula (B1a-38) is preferable.

Examples of the organic cation of Z1⁺ include an organic onium cation,an organic sulfonium cation, an organic iodonium cation, an organicammonium cation, a benzothiazolium cation and an organic phosphoniumcation. Of these, an organic sulfonium cation and an organic iodoniumcation are preferable, and an aryl sulfonium cation is more preferable.Specific examples thereof include a cation represented by any one offormula (b2-1) to formula (b2-4) (hereinafter sometimes referred to as“cation (b2-1)” according to the number of formula).

In formula (b2-1) to formula (b2-4),

R^(b4) to R^(b6) each independently represent a chain hydrocarbon grouphaving 1 to 30 carbon atoms, an alicyclic hydrocarbon group having 3 to36 carbon atoms or an aromatic hydrocarbon group having 6 to 36 carbonatoms, a hydrogen atom included in the chain hydrocarbon group may besubstituted with a hydroxy group, an alkoxy group having 1 to 12 carbonatoms, an alicyclic hydrocarbon group having 3 to 12 carbon atoms or anaromatic hydrocarbon group having 6 to 18 carbon atoms, a hydrogen atomincluded in the alicyclic hydrocarbon group may be substituted with ahalogen atom, an aliphatic hydrocarbon group having 1 to 18 carbonatoms, an alkylcarbonyl group having 2 to 4 carbon atoms or aglycidyloxy group, and a hydrogen atom included in the aromatichydrocarbon group may be substituted with a halogen atom, a hydroxygroup, an aliphatic hydrocarbon group having 1 to 18 carbon atoms, analkyl fluoride group having 1 to 12 carbon atoms or an alkoxy grouphaving 1 to 12 carbon atoms.

R^(b4) and R^(b5) may be bonded to each other to form a ring togetherwith sulfur atoms to which R^(b4) and R^(b5) are bonded, and —CH₂—included in the ring may be replaced by —O—, —S— or —CO—,

R^(b7) and R^(b8) each independently represent a halogen atom, a hydroxygroup, an aliphatic hydrocarbon group having 1 to 12 carbon atoms or analkoxy group having 1 to 12 carbon atoms,

m2 and n2 each independently represent an integer of 0 to 5,

when m2 is 2 or more, a plurality of R^(b7) may be the same ordifferent, and when n2 is 2 or more, a plurality of R^(b8) may be thesame or different,

R^(b9) and R^(b10) each independently represent a chain hydrocarbongroup having 1 to 36 carbon atoms or an alicyclic hydrocarbon grouphaving 3 to 36 carbon atoms,

R^(b9) and R^(b10) may be bonded to each other to form a ring togetherwith sulfur atoms to which R^(b9) and R^(b10) are bonded, and —CH₂—included in the ring may be replaced by —O—, —S— or —CO—,

R^(b11) represents a hydrogen atom, a chain hydrocarbon group having 1to 36 carbon atoms, an alicyclic hydrocarbon group having 3 to 36 carbonatoms or an aromatic hydrocarbon group having 6 to 18 carbon atoms,

R^(b12) represents a chain hydrocarbon group having 1 to 12 carbonatoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms or anaromatic hydrocarbon group having 6 to 18 carbon atoms, a hydrogen atomincluded in the chain hydrocarbon group may be substituted with anaromatic hydrocarbon group having 6 to 18 carbon atoms, a hydrogen atomincluded in the aromatic hydrocarbon group may be substituted with analkoxy group having 1 to 12 carbon atoms or an alkylcarbonyloxy grouphaving 1 to 12 carbon atoms,

R^(b11) and R^(b12) may be bonded to each other to form a ring,including —CH—CO— to which R^(b11) and R^(b12) are bonded, and —CH₂—included in the ring may be replaced by —O—, —S— or —CO—,

R^(b13) to R^(b18) each independently represent a halogen atom, ahydroxy group, an aliphatic hydrocarbon group having 1 to 12 carbonatoms or an alkoxy group having 1 to 12 carbon atoms,

L^(b31) represents a sulfur atom or an oxygen atom,

o2, p2, s2 and t2 each independently represent an integer of 0 to 5,

q2 and r2 each independently represent an integer of 0 to 4,

u2 represents 0 or 1, and

when o2 is 2 or more, a plurality of R^(b13) are the same or different,when p2 is 2 or more, a plurality of R^(b14) are the same or different,when q2 is 2 or more, a plurality of R^(b15) are the same or different,when r2 is 2 or more, a plurality of R^(b16) are the same or different,when s2 is 2 or more, a plurality of R^(b17) are the same or different,and when t2 is 2 or more, a plurality of R^(b18) are the same ordifferent.

The aliphatic hydrocarbon group represents a chain hydrocarbon group andan alicyclic hydrocarbon group.

Examples of the chain hydrocarbon group include alkyl groups such as amethyl group, an ethyl group, a propyl group, an isopropyl group, abutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, ahexyl group, an octyl group and a 2-ethylhexyl group.

Particularly, the chain hydrocarbon group of R^(b9) to R^(b12)preferably has 1 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either monocyclic or polycyclic,and examples of the monocyclic alicyclic hydrocarbon group includecycloalkyl groups such as a cyclopropyl group, a cyclobutyl group, acyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctylgroup and a cyclodecyl group. Examples of the polycyclic alicyclichydrocarbon group include a decahydronaphthyl group, an adamantyl group,a norbornyl group and the following groups.

Particularly, the alicyclic hydrocarbon group of R^(b9) to R^(b12)preferably has 3 to 18 carbon atoms, and more preferably 4 to 12 carbonatoms.

Examples of the alicyclic hydrocarbon group in which a hydrogen atom issubstituted with an aliphatic hydrocarbon group include amethylcyclohexyl group, a dimethylcyclohexyl group, a2-methyladamantan-2-yl group, a 2-ethyladamantan-2-yl group, a2-isopropyladamantan-2-yl group, a methylnorbornyl group, an isobornylgroup and the like. In the alicyclic hydrocarbon group in which ahydrogen atom is substituted with an aliphatic hydrocarbon group, thetotal number of carbon atoms of the alicyclic hydrocarbon group and thealiphatic hydrocarbon group is preferably 20 or less.

The alkyl fluoride group represents an alkyl group having 1 to 12 carbonatoms which has a fluorine atom, and examples thereof include afluoromethyl group, a difluoromethyl group, a trifluoromethyl group, aperfluorobutyl and the like. The number of carbon atoms of the alkylfluoride group is preferably 1 to 9, more preferably 1 to 6, still morepreferably 1 to 4.

Examples of the aromatic hydrocarbon group include aryl groups such as aphenyl group, a biphenyl group, a naphthyl group and a phenanthrylgroup. The aromatic hydrocarbon group may have a chain hydrocarbon groupor an alicyclic hydrocarbon group, and examples thereof include anaromatic hydrocarbon group having a chain hydrocarbon group (a tolylgroup, a xylyl group, a cumenyl group, a mesityl group, a p-ethylphenylgroup, a p-tert-butylphenyl group, a 2,6-diethylphenyl group, a2-methyl-6-ethylphenyl group, etc.) and an aromatic hydrocarbon grouphaving an alicyclic hydrocarbon group (a p-cyclohexylphenyl group, ap-adamantylphenyl group, etc.).

When the aromatic hydrocarbon group has a chain hydrocarbon group or analicyclic hydrocarbon group, a chain hydrocarbon group having 1 to 18carbon atoms and an alicyclic hydrocarbon group having 3 to 18 carbonatoms are preferable.

Examples of the aromatic hydrocarbon group in which a hydrogen atom issubstituted with an alkoxy group include a p-methoxyphenyl group and thelike.

Examples of the chain hydrocarbon group in which a hydrogen atom issubstituted with an aromatic hydrocarbon group include aralkyl groupssuch as a benzyl group, a phenethyl group, a phenylpropyl group, atrityl group, a naphthylmethyl group and a naphthylethyl group.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, aheptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxygroup.

Examples of the alkylcarbonyl group include an acetyl group, a propionylgroup and a butyryl group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of the alkylcarbonyloxy group include a methylcarbonyloxygroup, an ethylcarbonyloxy group, a propylcarbonyloxy group, anisopropylcarbonyloxy group, a butylcarbonyloxy group, asec-butylcarbonyloxy group, a tert-butylcarbonyloxy group, apentylcarbonyloxy group, a hexylcarbonyloxy group, an octylcarbonyloxygroup and a 2-ethylhexylcarbonyloxy group.

The ring formed by bonding R^(b4) and R^(b5) each other, together withsulfur atoms to which R^(b4) and R^(b5) are bonded, may be a monocyclic,polycyclic, aromatic, nonaromatic, saturated or unsaturated ring. Thisring includes a ring having 3 to 18 carbon atoms and is preferably aring having 4 to 18 carbon atoms. The ring containing a sulfur atomincludes a 3-membered to 12-membered ring and is preferably a 3-memberedto 7-membered ring and includes, for example, the following rings andthe like. * represents a bond.

The ring formed by combining R^(b9) and R^(b10) together may be amonocyclic, polycyclic, aromatic, nonaromatic, saturated or unsaturatedring. This ring includes a 3-membered to 12-membered ring and ispreferably a 3-membered to 7-membered ring. The ring includes, forexample, a thiolan-1-ium ring (tetrahydrothiophenium ring), athian-1-ium ring, a 1,4-oxathian-4-ium ring and the like.

The ring formed by combining R^(b11) and R^(b12) together may be amonocyclic, polycyclic, aromatic, nonaromatic, saturated or unsaturatedring. This ring includes a 3-membered to 12-membered ring and ispreferably a 3-membered to 7-membered ring. Examples thereof include anoxocycloheptane ring, an oxocyclohexane ring, an oxonorbornane ring, anoxoadamantane ring and the like.

Of cation (b2-1) to cation (b2-4), a cation (b2-1) is preferable.

Examples of the cation (b2-1) include the following cations.

Examples of the cation (b2-2) include the following cations.

Examples of the cation (b2-3) include the following cations.

Examples of the cation (b2-4) include the following cations.

The acid generator (B) is a combination of the anion mentioned above andthe organic cation mentioned above, and these can be optionallycombined. The acid generator (B) preferably includes a combination of ananion represented by any one of formula (B1a-1) to formula (B1a-3),formula (B1a-7) to formula (B1a-16), formula (B1a-18), formula (B1a-19)and formula (B1a-22) to formula (B1a-38) with a cation (b2-1), a cation(b2-3) or a cation (b2-4).

The acid generator (B) preferably includes those represented by formula(B1-1) to formula (B1-56). Of these acid generators, those containing anarylsulfonium cation are preferable and those represented by formula(B1-1) to formula (B1-3), formula (B1-5) to formula (B1-7), formula(B1-11) to formula (B1-14), formula (B1-20) to formula (B1-26), formula(B1-29) and formula (B1-31) to formula (B1-56) are particularlypreferable.

In the resist composition according to some embodiments of the presentdisclosure, the content of the acid generator is preferably 1 part bymass or more and 45 parts by mass or less, more preferably 1 part bymass or more and 40 parts by mass or less, still more preferably 3 partsby mass or more and 40 parts by mass or less, and yet more preferably 10parts by mass or more and 40 parts by mass or less, based on 100 partsby mass of the below-mentioned resin (A).

<Solvent (E)>

The content of the solvent (E) in the resist composition is usually 90%by mass or more and 99.9% by mass or less, preferably 92% by mass ormore and 99% by mass or less, and more preferably 94% by mass or moreand 99% by mass or less. The content of the solvent (E) can be measured,for example, by a known analysis means such as liquid chromatography orgas chromatography.

Examples of the solvent (E) include glycol ether esters such asethylcellosolve acetate, methylcellosolve acetate and propylene glycolmonomethyl ether acetate; glycol ethers such as propylene glycolmonomethyl ether; esters such as ethyl lactate, butyl acetate, amylacetate and ethyl pyruvate; ketones such as acetone, methyl isobutylketone, 2-heptanone and cyclohexanone; and cyclic esters such asγ-butyrolactone. The solvent (E) may be used alone, or two or moresolvents may be used.

<Quencher (C)>

Examples of the quencher (C) include a basic nitrogen-containing organiccompound, and a salt generating an acid having an acidity lower thanthat of an acid generated from an acid generator (B). When the resistcomposition includes the quencher (C), the content of the quencher (C)is preferably about 0.01 to 15% by mass, more preferably about 0.01 to10% by mass, still more preferably about 0.1 to 5% by mass, and yet morepreferably about 0.1 to 3% by mass, based on the amount of the solidcomponent of the resist composition.

Examples of the basic nitrogen-containing organic compound include amineand an ammonium salt. Examples of the amine include an aliphatic amineand an aromatic amine. Examples of the aliphatic amine include a primaryamine, a secondary amine and a tertiary amine.

Examples of the amine include 1-naphthylamine, 2-naphthylamine, aniline,diisopropylaniline, 2-, 3- or 4-methylaniline, 4-nitroaniline,N-methylaniline, N,N-dimethylaniline, diphenylamine, hexylamine,heptylamine, octylamine, nonylamine, decylamine, dibutylamine,dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine,didecylamine, triethylamine, trimethylamine, tripropylamine,tributylamine, tripentylamine, trihexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, methyldibutylamine,methyldipentylamine, methyldihexylamine, methyldicyclohexylamine,methyldiheptylamine, methyldioctylamine, methyldinonylamine,methyldidecylamine, ethyldibutylamine, ethyldipentylamine,ethyldihexylamine, ethyldiheptylamine, ethyldioctylamine,ethyldinonylamine, ethyldidecylamine, dicyclohexylmethylamine,tris[2-(2-methoxyethoxy)ethyl]amine, triisopropanolamine,ethylenediamine, tetramethylenediamine, hexamethylenediamine,4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane,4,4′-diamino-3,3′-diethyldiphenylmethane, 2,2′-methylenebisaniline,imidazole, 4-methylimidazole, pyridine, 4-methylpyridine,1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene,1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy)ethane,di(2-pyridyl)ketone, 4,4′-dipyridyl sulfide, 4,4′-dipyridyl disulfide,2,2′-dipyridylamine, 2,2′-dipicolylamine, bipyridine and the like,preferably diisopropylaniline, and more preferably2,6-diisopropylaniline.

Examples of the ammonium salt include tetramethylammonium hydroxide,tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide,tetrahexylammonium hydroxide, tetraoctylammonium hydroxide,phenyltrimethylammonium hydroxide,3-(trifluoromethyl)phenyltrimethylammonium hydroxide,tetra-n-butylammonium salicylate and choline.

The acidity in a salt generating an acid having an acidity lower thanthat of an acid generated from the acid generator (B) is indicated bythe acid dissociation constant (pKa). Regarding the salt generating anacid having an acidity lower than that of an acid generated from theacid generator (B), the acid dissociation constant of an acid generatedfrom the salt usually meets the following inequality: −3<pKa, preferably−1<pKa<7, and more preferably 0<pKa<5.

Examples of the salt generating an acid having an acidity lower thanthat of an acid generated from the acid generator (B) include saltsrepresented by the following formulas, a salt represented by formula (D)mentioned in JP 2015-147926 A (hereinafter sometimes referred to as“weak acid inner salt (D)”, and salts mentioned in JP 2012-229206 A, JP2012-6908 A, JP 2012-72109 A, JP 2011-39502 A and JP 2011-191745 A. Thesalt is preferably a salt generating a carboxylic acid having an aciditylower than that of an acid generated from the acid generator (B) (salthaving a carboxylic acid anion), and more preferably a weak acid innersalt (D).

Examples of the weak acid inner salt (D) include the following salts.

<Other Components>

The resist composition according to some embodiments of the presentdisclosure may also include components other than the componentsmentioned above (hereinafter sometimes referred to as “other components(F)”), if necessary. The other components (F) are not particularlylimited and it is possible to use various additives known in the resistfield, for example, sensitizers, dissolution inhibitors, surfactants,stabilizers and dyes.

<Preparation of Resist Composition>

The resist composition according to some embodiments of the presentdisclosure can be prepared by mixing a compound (I), a resin (A) and anacid generator (B), and if necessary, resins other than the resin (A) tobe used, a solvent (E), a quencher (C) and other components (F). Theorder of mixing these components is any order and is not particularlylimited. It is possible to select, as the temperature during mixing,appropriate temperature from 10 to 40° C., according to the type of theresin, the solubility in the solvent (E) of the resin and the like. Itis possible to select, as the mixing time, appropriate time from 0.5 to24 hours according to the mixing temperature. The mixing means is notparticularly limited and it is possible to use mixing with stirring.

After mixing the respective components, the mixture is preferablyfiltered through a filter having a pore diameter of about 0.003 to 0.2μm.

(Method for Producing Resist Pattern)

The method for producing a resist pattern according to some embodimentsof the present disclosure includes:

(1) a step of applying the resist composition according to someembodiments of the present disclosure on a substrate,

(2) a step of drying the applied resist composition to form acomposition layer,

(3) a step of exposing the composition layer,

(4) a step of heating the exposed composition layer, and

(5) a step of developing the heated composition layer.

The resist composition can be usually applied on a substrate using aconventionally used apparatus, such as a spin coater. Examples of thesubstrate include inorganic substrates such as a silicon wafer. Beforeapplying the resist composition, the substrate may be washed, and anorganic antireflection film may be formed on the substrate.

The solvent is removed by drying the applied composition to form acomposition layer. Drying is performed by evaporating the solvent usinga heating device such as a hot plate (so-called “prebake”), or adecompression device. The heating temperature is preferably 50 to 200°C. and the heating time is preferably 10 to 180 seconds. The pressureduring drying under reduced pressure is preferably about 1 to 1.0×10⁵Pa.

The composition layer thus obtained is usually exposed using an aligner.The aligner may be a liquid immersion aligner. It is possible to use, asan exposure source, various exposure sources, for example, exposuresources capable of emitting laser beam in an ultraviolet region such asKrF excimer laser (wavelength of 248 nm), ArF excimer laser (wavelengthof 193 nm) and F₂ excimer laser (wavelength of 157 nm), an exposuresource capable of emitting harmonic laser beam in a far-ultraviolet orvacuum ultra violet region by wavelength-converting laser beam from asolid-state laser source (YAG or semiconductor laser), an exposuresource capable of emitting electron beam or EUV and the like. In thepresent specification, such exposure to radiation is sometimescollectively referred to as “exposure”. The exposure is usuallyperformed through a mask corresponding to a pattern to be required. Whenelectron beam is used as the exposure source, exposure may be performedby direct writing without using the mask.

The exposed composition layer is subjected to a heat treatment(so-called “post-exposure bake”) to promote the deprotection reaction inan acid-labile group. The heating temperature is usually about 50 to200° C., and preferably about 70 to 150° C.

The heated composition layer is usually developed with a developingsolution using a development apparatus. Examples of the developingmethod include a dipping method, a paddle method, a spraying method, adynamic dispensing method and the like. The developing temperature ispreferably, for example, 5 to 60° C. and the developing time ispreferably, for example, 5 to 300 seconds. It is possible to produce apositive resist pattern or negative resist pattern by selecting the typeof the developing solution as follows.

When the positive resist pattern is produced from the resist compositionaccording to some embodiments of the present disclosure, an alkalinedeveloping solution is used as the developing solution. The alkalinedeveloping solution may be various aqueous alkaline solutions used inthis field. Examples thereof include aqueous solutions oftetramethylammonium hydroxide and (2-hydroxyethyl)trimethylammoniumhydroxide (commonly known as choline). The surfactant may be containedin the alkaline developing solution.

It is preferable that the developed resist pattern is washed withultrapure water and then water remaining on the substrate and thepattern is removed.

When the negative resist pattern is produced from the resist compositionaccording to some embodiments of the present disclosure, a developingsolution containing an organic solvent (hereinafter sometimes referredto as “organic developing solution”) is used as the developing solution.

Examples of the organic solvent contained in the organic developingsolution include ketone solvents such as 2-hexanone and 2-heptanone;glycol ether ester solvents such as propylene glycol monomethyl etheracetate; ester solvents such as butyl acetate; glycol ether solventssuch as propylene glycol monomethyl ether; amide solvents such asN,N-dimethylacetamide; and aromatic hydrocarbon solvents such asanisole.

The content of the organic solvent in the organic developing solution ispreferably 90% by mass or more and 100% by mass or less, more preferably95% by mass or more and 100% by mass or less, and still more preferablythe organic developing solution is substantially composed of the organicsolvent.

Particularly, the organic developing solution is preferably a developingsolution containing butyl acetate and/or 2-heptanone. The total contentof butyl acetate and 2-heptanone in the organic developing solution ispreferably 50% by mass or more and 100% by mass or less, more preferably90% by mass or more and 100% by mass or less, and still more preferablythe organic developing solution is substantially composed of butylacetate and/or 2-heptanone.

The surfactant may be contained in the organic developing solution. Atrace amount of water may be contained in the organic developingsolution.

During development, the development may be stopped by replacing by asolvent with the type different from that of the organic developingsolution.

The developed resist pattern is preferably washed with a rinsingsolution. The rinsing solution is not particularly limited as long as itdoes not dissolve the resist pattern, and it is possible to use asolution containing an ordinary organic solvent which is preferably analcohol solvent or an ester solvent.

After washing, the rinsing solution remaining on the substrate and thepattern is preferably removed.

(Application)

The resist composition according to some embodiments of the presentdisclosure is suitable as a resist composition for exposure of KrFexcimer laser, a resist composition for exposure of ArF excimer laser, aresist composition for exposure of electron beam (EB) or a resistcomposition for exposure of EUV, particularly a resist composition forexposure of electron beam (EB) or a resist composition for exposure ofEUV, and the resist composition is useful for fine processing ofsemiconductors.

EXAMPLES

Some embodiments of the present disclosure will be described morespecifically by way of Examples. Percentages and parts expressing thecontents or amounts used in the Examples are by mass unless otherwisespecified.

The weight-average molecular weight is a value determined by gelpermeation chromatography under the following conditions.

Apparatus: Model HLC-8120GPC (manufactured by TOSOH CORPORATION)

Column: TSKgel Multipore IIXL-M×3+guardcolumn (manufactured by TOSOHCORPORATION)

Eluent: tetrahydrofuran

Flow rate: 1.0 mL/min

Detector: RI detector

Column temperature: 40° C.

Injection amount: 100 μl

Molecular weight standards: polystyrene standard (manufactured by TOSOHCORPORATION)

Structures of compounds were confirmed by measuring a molecular ion peakusing mass spectrometry (Liquid Chromatography: Model 1100, manufacturedby Agilent Technologies, Inc., Mass Spectrometry: Model LC/MSD,manufactured by Agilent Technologies, Inc.). The value of this molecularion peak in the following Examples is indicated by “MASS”.

Synthesis of Resin

Compounds (monomers) used in synthesis of a resin (A) are shown below.Hereinafter, these compounds are referred to as “monomer (a1-1-3)”according to the formula number.

Synthesis Example 1 [Synthesis of Resin A1]

Using a monomer (a1-1-3), a monomer (a1-2-6), a monomer (a2-1-3), amonomer (a3-4-2) and a monomer (a1-4-2) as monomers, these monomers weremixed in a molar ratio of 20:35:3:15:27 [monomer (a1-1-3):monomer(a1-2-6):monomer (a2-1-3):monomer (a3-4-2):monomer (a1-4-2)], and thismonomer mixture was further mixed with methyl isobutyl ketone in theamount of 1.5 mass times the total mass of all monomers. To the mixturethus obtained, azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) as initiators were added in theamounts of 1.2 mol % and 3.6 mol % based on the total molar number ofall monomers, followed by heating at 73° C. for about 5 hours.Thereafter, to the polymerization reaction solution thus obtained, anaqueous p-toluenesulfonic acid solution (2.5% by weight) was added inthe amount of 2.0 mass times the total mass of all monomers, followed bystirring for 12 hours and further isolation through separation. Theorganic layer thus recovered was poured into a large amount of n-heptaneto precipitate a resin, followed by filtration and recovery to obtain aresin A1 having a weight-average molecular weight of about 5.3×10³ in ayield of 63%. This resin A1 has the following structural units.

Synthesis Example 2 [Synthesis of Resin A2]

Using a monomer (a1-1-3), a monomer (a1-2-6), a monomer (a2-1-3), amonomer (a3-4-2) and a monomer (a1-4-13) as monomers, these monomerswere mixed in a molar ratio of 20:35:3:15:27 [monomer (a1-1-3):monomer(a1-2-6):monomer (a2-1-3):monomer (a3-4-2):monomer (a1-4-13)], and thismonomer mixture was further mixed with methyl isobutyl ketone in theamount of 1.5 mass times the total mass of all monomers. To the mixturethus obtained, azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) as initiators were added in theamounts of 1.2 mol % and 3.6 mol % based on the total molar number ofall monomers, followed by heating at 73° C. for about 5 hours.Thereafter, to the polymerization reaction solution thus obtained, anaqueous p-toluenesulfonic acid solution (2.5% by weight) was added inthe amount of 2.0 mass times the total mass of all monomers, followed bystirring for 12 hours and further isolation through separation.Thereafter, the reaction solution was poured into a large amount ofn-heptane to precipitate a resin, followed by filtration and recovery toobtain a resin A2 having a weight-average molecular weight of about5.1×10³ in a yield of 61%. This resin A2 has the following structuralunits.

<Preparation of Resist Composition>

As shown in Table 1, the following components were mixed and the mixturethus obtained was filtered through a fluororesin filter having a porediameter of 0.2 μm to prepare resist compositions.

TABLE 1 Resist composition Resin Acid generator(B) Compound (I) Quencher(C) PB/PEB Composition 1 A1 = 10 parts B1-43 = 3.4 parts I-2 = 0.2 partC1 = 0.7 part 100° C./100° C. Composition 2 A2 = 10 parts B1-43 = 3.4parts I-2 = 0.2 part C1 = 0.7 part 100° C./100° C. Composition 3 A1 = 10parts B1-43 = 3.4 parts I-3 = 0.2 part C1 = 0.7 part 100° C./100° C.Composition 4 A2 = 10 parts B1-43 = 3.4 parts I-3 = 0.2 part C1 = 0.7part 100° C./100° C. Composition 5 A1 = 10 parts B1-43 = 3.4 parts I-4 =0.2 part C1 = 0.7 part 100° C./100° C. Composition 6 A2 = 10 parts B1-43= 3.4 parts I-4 = 0.2 part C1 = 0.7 part 100° C./100° C. Composition 7A1 = 10 parts B1-43 = 3.4 parts I-9 = 0.2 part C1 = 0.7 part 100°C./100° C. Composition 8 A2 = 10 parts B1-43 = 3.4 parts I-9 = 0.2 partC1 = 0.7 part 100° C./100° C. Composition 9 A1 = 10 parts B1-43 = 3.4parts I-10 = 0.2 part C1 = 0.7 part 100° C./100° C. Composition 10 A2 =10 parts B1-43 = 3.4 parts I-10 = 0.2 part C1 = 0.7 part 100° C./100° C.Composition 11 A1 = 10 parts B1-43 = 3.4 parts I-1 = 0.2 part C1 = 0.7part 100° C./100° C. Composition 12 A1 = 10 parts B1-43 = 3.4 parts I-12= 0.2 part C1 = 0.7 part 100° C./100° C. Composition 13 A1 = 10 partsB1-43 = 3.4 parts I-17 = 0.2 part C1 = 0.7 part 100° C./100° C.Composition 14 A1 = 10 parts B1-43 = 3.4 parts I-18 = 0.2 part C1 = 0.7part 100° C./100° C. Composition 15 A1 = 10 parts B1-43 = 3.4 parts I-23= 0.2 part C1 = 0.7 part 100° C./100° C. Composition 16 A1 = 10 partsB1-43 = 3.4 parts I-24 = 0.2 part C1 = 0.7 part 100° C./100° C.Composition 17 A1 = 10 parts B1-43 = 3.4 parts I-25 = 0.2 part C1 = 0.7part 100° C./100° C. Composition 18 A1 = 10 parts B1-43 = 3.4 parts I-26= 0.2 part C1 = 0.7 part 100° C./100° C. Composition 19 A1 = 10 partsB1-43 = 3.4 parts I-28 = 0.2 part C1 = 0.7 part 100° C./100° C.Comparative A1 = 10 parts B1-43 = 3.4 parts IX-1 = 0.2 part C1 = 0.7part 100° C./100° C. Composition 1<Resin>

A1: Resin A1

<Acid Generator (B)>

B1-43: Salt represented by formula (B1-43) (synthesized in accordancewith Examples of JP 2016-47815 A)

<Compound (I)>

I-1: Compound represented by formula (I-1)

I-2: Compound represented by formula (I-2)

I-3: Compound represented by formula (I-3)

I-4: Compound represented by formula (I-4)

I-9: Compound represented by formula (I-9)

I-10: Compound represented by formula (I-10)

I-12: Compound represented by formula (I-12)

I-17: Compound represented by formula (I-17)

I-18: Compound represented by formula (I-18)

I-23: Compound represented by formula (I-23)

I-24: Compound represented by formula (I-24)

I-25: Compound represented by formula (I-25)

I-26: Compound represented by formula (I-26)

I-28: Compound represented by formula (I-28)

IX-1: Compound represented by formula (IX-1)

<Quencher (C)>

C1: synthesized by the method mentioned in JP 2011-39502 A

<Solvent>

Propylene glycol monomethyl ether acetate 400 parts Propylene glycolmonomethyl ether 100 parts γ-Butyrolactone 5 parts(Evaluation of Exposure of Resist Composition with Electron Beam)

Each 6 inch-diameter silicon wafer was treated with hexamethyldisilazaneon a direct hot plate at 90° C. for 60 seconds. A resist composition wasspin-coated on the silicon wafer in such a manner that the thickness ofthe composition later became 0.04 μm. Then, the coated silicon wafer wasprebaked on the direct hot plate at the temperature shown in the column“PB” of Table 1 for 60 seconds to form a composition layer. Using anelectron-beam direct-write system (“ELS-F125 125 keV”, manufactured byELIONIX INC.), contact hole patterns (hole pitch of 40 nm/hole diameterof 17 nm) were directly written on the composition layer formed on thewafer while changing the exposure dose stepwise.

After exposure, post-exposure baking was performed on the hot plate atthe temperature shown in the column “PEB” of Table 1 for 60 seconds.Then, this composition layer on the silicon wafer was developed withbutyl acetate (manufactured by Tokyo Chemical Industry Co., Ltd.) as adeveloper at 23° C. for 20 seconds using the dynamic dispensing methodto obtain a resist pattern.

In the resist pattern obtained after development, the exposure dose atwhich the diameter of holes formed became 17 nm was defined as effectivesensitivity.

<Evaluation of CD Uniformity (CDU)>

In the effective sensitivity, the hole diameter of the pattern formedwith a hole dimeter of 17 nm was determined by measuring 24 times perone hole and the average of the measured values was regarded as theaverage hole diameter. The standard deviation was determined under theconditions that the average diameter of 400 holes about the patternsformed with a hole dimeter of 17 nm in the same wafer was regarded to aspopulation.

The results are shown in Table 2. The numerical value in the parenthesisrepresents the standard deviation (nm).

TABLE 2 Resist composition CDU Example 1  Composition 1  2.59 Example 2 Composition 2  2.50 Example 3  Composition 3  2.61 Example 4 Composition 4  2.53 Example 5  Composition 5  2.55 Example 6 Composition 6  2.48 Example 7  Composition 7  2.49 Example 8 Composition 8  2.41 Example 9  Composition 9  2.51 Example 10Composition 10 2.43 Example 11 Composition 11 2.63 Example 12Composition 12 2.48 Example 13 Composition 13 2.44 Example 14Composition 14 2.36 Example 15 Composition 15 2.46 Example 16Composition 16 2.42 Example 17 Composition 17 2.34 Example 18Composition 18 2.49 Example 19 Composition 19 2.50 Comparative Example 1Comparative Composition 1 2.88

As compared with Comparative Composition 1, Compositions 1 to 19exhibited small standard deviation and satisfactory evaluation of CDuniformity (CDU).

INCORPORATION BY REFERENCE

Priority is claimed on Japanese application No. 2020-037661, filed Mar.5, 2020 the content of which is incorporated herein by reference.

The invention claimed is:
 1. A resist composition comprising a compoundrepresented by formula (I), a resin having an acid-labile group, an acidgenerator, and a salt generating an acid having an acidity lower thanthat of an acid generated from the acid generator:

wherein, in formula (I), R¹ represents a halogen atom or an alkylfluoride group having 1 to 6 carbon atoms, m1 represents an integer of 1to 5, and when m1 is 2 or more, a plurality of R¹ may be the same ordifferent from each other.
 2. The resist composition according to claim1, wherein R¹ is a fluorine atom, an iodine atom or a trifluoromethylgroup.
 3. The resist composition according to claim 1, wherein m1 is aninteger of 1 to
 3. 4. The resist composition according to claim 3,wherein R¹ includes at least an iodine atom.
 5. The resist compositionaccording to claim 1, wherein the content of the compound (I) is 0.001to 20% by mass based on the solid content.
 6. The resist compositionaccording to claim 1, wherein the resin having the acid-labile groupincludes at least one selected from a group consisting of a structuralunit represented by formula (a1-1) and a structural unit represented byformula (a1-2):

wherein, in formula (a1-1) and formula (a1-2), L^(a1) and L^(a2) eachindependently represent —O— or *—O—(CH₂)_(k1)—CO—O—, and k1 representsan integer of 1 to 7, * represents a bond to —CO—, R^(a4) and R^(a5)each independently represent a hydrogen atom, a halogen atom, or analkyl group having 1 to 6 carbon atoms which may have a halogen atom,R^(a6) and R^(a7) each independently represent an alkyl group having 1to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, analicyclic hydrocarbon group having 3 to 18 carbon atoms, an aromatichydrocarbon group having 6 to 18 carbon atoms, or a group obtained bycombining these groups, m1 represents an integer of 0 to 14, n1represents an integer of 0 to 10, and n1′ represents an integer of 0 to3.
 7. The resist composition according to claim 6, wherein the resinhaving the acid-labile group includes the structural unit represented byformula (a1-1).
 8. The resist composition according to claim 6, whereinthe resin having the acid-labile group includes the structural unitrepresented by formula (a1-2).
 9. The resist composition according toclaim 6, wherein the resin having the acid-labile group includes atleast one structural unit represented by formula (a1-1) and includes atleast one structural unit represented by formula (a1-2).
 10. The resistcomposition according to claim 1, wherein the resin having theacid-labile group includes a structural unit represented by formula(a2-A):

wherein, in formula (a2-A), R^(a50) represents a hydrogen atom, ahalogen atom, or an alkyl group having 1 to 6 carbon atoms which mayhave a halogen atom, R^(a51) represents a halogen atom, a hydroxy group,an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, analkoxyalkoxy group having 2 to 12 carbon atoms, an alkylcarbonyl grouphaving 2 to 4 carbon atoms, an alkylcarbonyloxy group having 2 to 4carbon atoms, an acryloyloxy group or a methacryloyloxy group, A^(a50)represents a single bond or *—X^(a51)-(A^(a52)-X^(a52))_(nb)—, and *represents a bond to carbon atoms to which —R^(a50) is bonded, A^(a52)represents an alkanediyl group having 1 to 6 carbon atoms, X^(a51) andX^(a52) each independently represent —O—, —CO—O— or —O—CO—, nbrepresents 0 or 1, and mb represents an integer of 0 to 4, and when mbis an integer of 2 or more, a plurality of R^(a51) may be the same ordifferent from each other.
 11. The resist composition according to claim1, wherein the acid generator includes a salt represented by formula(B1):

wherein, in formula (B1), Q^(b1) and Q^(b2) each independently representa fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms,L^(b1) represents a divalent saturated hydrocarbon group having 1 to 24carbon atoms, —CH₂— included in the divalent saturated hydrocarbon groupmay be replaced by —O— or —CO—, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group, Y represents a methyl group which may have asubstituent, or an alicyclic hydrocarbon group having 3 to 24 carbonatoms which may have a substituent, and —CH₂— included in the alicyclichydrocarbon group may be replaced by —O—, —S(O)₂— or —CO—, and Z⁺represents an organic cation.
 12. The resist composition according toclaim 1, wherein the acid dissociation constant of an acid generatedfrom the salt generating an acid having an acidity lower than that of anacid generated from the acid generator meets −1<pKa<7.
 13. The resistcomposition according to claim 1, wherein the salt generating an acidhaving an acidity lower than that of an acid generated from the acidgenerator is at least one of the following salts:


14. The resist composition according to claim 1, wherein m1 is 3, andone of the three R¹s bonded to the para-position with respect to acarboxy group of the benzene ring, two of the three R¹s bonded to themeta-position with respect to a carboxy group of the benzene ring. 15.The resist composition according to claim 1, wherein at least one R¹ isan iodine atom, and the iodine atom bonded to the para-position withrespect to a carboxy group of the benzene ring.
 16. The resistcomposition according to claim 1, wherein at least two R¹s are an iodineatom, and the iodine atom each bonded to the meta-position with respectto a carboxy group of the benzene ring.
 17. The resist compositionaccording to claim 1, wherein the compound represented by formula (I) isat least one of the following compounds:


18. A method for producing a resist pattern, which comprises: (1) a stepof applying the resist composition according to claim 1 on a substrate,(2) a step of drying the applied resist composition to form acomposition layer, (3) a step of exposing the composition layer, (4) astep of heating the exposed composition layer, and (5) a step ofdeveloping the heated composition layer.